RTonc.Site
Q1 (2022 Exam)
1 Ci is equal to:
A) 2.7 × 10¹⁰ Bq
B) 3.7 × 10¹⁰ Bq (Correct Answer)
C) 3.7 × 10⁹ Bq
D) 2.7 Bq
Explanation:
1 Curie equals 3.7 × 10¹⁰ disintegrations per second; this is the standard SI conversion value.
Q2 (2022 Exam)
Cathode rays are:
A) Electromagnetic waves
B) Moving electrons (Correct Answer)
C) Moving negative ions
D) None of the above
Explanation:
Cathode rays are streams of electrons emitted from the cathode in a vacuum tube.
Q3 (2022 Exam)
Radioactive substance does not emit:
A) Electromagnetic radiation
B) Electrons
C) Protons (Correct Answer)
D) None of the above
Explanation:
Common radioactive decays emit α, β, or γ radiation; proton emission is rare.
Q4 (2022 Exam)
Rest mass of electron is:
A) 930 MeV
B) 931 MeV
C) 0.511 MeV (Correct Answer)
D) 511 MeV
Explanation:
Electron rest energy is 0.511 MeV (equivalent to 9.11 × 10⁻³¹ kg).
Q5 (2022 Exam)
In an electrical circuit an ammeter is connected in:
A) Parallel
B) Series (Correct Answer)
C) None of the above
D) Both of the above
Explanation:
An ammeter must be connected in series to measure the current flowing through the circuit.
Q6 (2022 Exam)
In ⁶⁰Co the mass number is:
A) 27
B) 33
C) 60 (Correct Answer)
D) 87
Explanation:
The isotope ⁶⁰Co has a mass number of 60 and an atomic number of 27.
Q7 (2022 Exam)
The unit of magnetic flux is:
A) Volt
B) Weber (Correct Answer)
C) Tesla
D) Curie
Explanation:
Weber (Wb) is the SI unit of magnetic flux; 1 Wb = 1 T·m².
Q8 (2022 Exam)
Half life of Ir-192 is:
A) 5.26 years
B) 14 days
C) 74 days (Correct Answer)
D) 30 years
Explanation:
Iridium-192 has a half-life of approximately 74 days.
Q9 (2022 Exam)
The circuit required to convert AC to DC is:
A) Filter
B) Rectifier (Correct Answer)
C) Amplifier
D) None of the above
Explanation:
Rectifiers use diodes to convert alternating current to direct current.
Q10 (2022 Exam)
Which of the following wavelength falls in the range of X-rays?
A) 0.1 Å (Correct Answer)
B) 100 nm
C) 1 cm
D) 1 meter
Explanation:
X-rays have wavelengths between 0.01 Å and 10 Å.
Q11 (2022 Exam)
What value of n will make this proportion 6 : 15 = n : 25 ?
A) 10 (Correct Answer)
B) 15
C) 18
D) 25
Explanation:
n = (6 × 25) / 15 = 10.
Q12 (2022 Exam)
Auger electron is associated with:
A) Photoelectric Effect (Correct Answer)
B) Compton Effect
C) Pair Production
D) None of the above
Explanation:
An Auger electron is ejected when excess energy from an inner-shell transition is transferred to another electron.
Q13 (2022 Exam)
Neutrino is associated with:
A) Alpha emission
B) Beta emission (Correct Answer)
C) Gamma emission
D) Elastic scattering
Explanation:
Beta decay involves emission of a neutrino or antineutrino along with an electron or positron.
Q14 (2022 Exam)
Power factor in purely inductive circuit:
A) 1
B) 0 (Correct Answer)
C) 10
D) None of the above
Explanation:
In a pure inductor, current lags voltage by 90°, making power factor zero.
Q15 (2022 Exam)
In 5th generation CT:
A) X-ray source rotates alone
B) Detector rotates alone
C) Detector and X-ray source both rotate (Correct Answer)
D) None of the above
Explanation:
In later CT generations, both X-ray tube and detectors rotate around the patient.
Q16 (2022 Exam)
The electric potential of Earth is taken as:
A) Zero (Correct Answer)
B) Infinite
C) Unity
D) None of the above
Explanation:
By convention, Earth is considered to have zero electric potential.
Q17 (2022 Exam)
Tenth value of lead for Co-60 gamma ray is:
A) 2.58 × 10⁻⁴ C/kg
B) 3.6 cm (Correct Answer)
C) 0.827 cm
D) None of the above
Explanation:
The tenth value layer (TVL) for Co-60 gamma rays in lead is about 3.6 cm.
Q18 (2022 Exam)
The Co-60 source in teletherapy machine is:
A) Accelerator produced
B) Reactor produced (Correct Answer)
C) Both
D) None of the above
Explanation:
Cobalt-60 is produced in nuclear reactors by neutron activation of cobalt-59.
Q19 (2022 Exam)
Which of the following can pass through 20 cm thickness of steel?
A) Alpha particle
B) Beta particle
C) Gamma rays (Correct Answer)
D) None of the above
Explanation:
Gamma rays have high penetration power and can pass through dense materials like steel.
Q20 (2022 Exam)
1 Farad is equivalent to:
A) 1 C / 1 V (Correct Answer)
B) 1 V / 1 C
C) 19 / 1 C
D) None of the above
Explanation:
1 Farad = 1 Coulomb per Volt, the unit of capacitance.
Q21 (2021 Exam)
Rest mass of electron is:
A) 930 MeV
B) 931 MeV
C) 0.511 MeV (Correct Answer)
D) None of the above
Explanation:
The rest energy of an electron is 0.511 MeV.
Q22 (2021 Exam)
The electric potential of Earth is taken as:
A) Zero (Correct Answer)
B) Infinite
C) Unity
D) None of the above
Explanation:
By convention, the Earth’s potential is zero.
Q23 (2021 Exam)
Which of the following rule is obeyed in the decay of radioactive substances?
A) Proportional
B) Exponential (Correct Answer)
C) Inversely proportional
D) None of the above
Explanation:
Radioactive decay follows an exponential law.
Q24 (2021 Exam)
The SI unit of magnetic field strength is:
A) Volt
B) Weber
C) Tesla (Correct Answer)
D) None of the above
Explanation:
Magnetic flux density is measured in Tesla (T).
Q25 (2021 Exam)
Half-life of Ir-192 is:
A) 5.26 yr
B) 14 days
C) 74 days (Correct Answer)
D) 78 days
Explanation:
Ir-192 has a half-life of approximately 74 days.
Q26 (2021 Exam)
The melting point of tungsten is:
A) 2200°C
B) 3370°C (Correct Answer)
C) 4470°C
D) None of the above
Explanation:
Tungsten melts at about 3370°C, used for X-ray tube filaments.
Q27 (2021 Exam)
Tenth value layer of lead for Co-60 gamma rays is:
A) 2.58 × 10⁻⁴ C/kg in air
B) 3.6 cm (Correct Answer)
C) 0.827 cm
D) None of the above
Explanation:
For Co-60 gamma, TVL in lead is about 3.6 cm.
Q28 (2021 Exam)
The Co-60 source in a teletherapy machine is:
A) Accelerator produced
B) Reactor produced (Correct Answer)
C) Both
D) None of the above
Explanation:
Cobalt-60 is produced by neutron activation of cobalt-59 in reactors.
Q29 (2021 Exam)
Which of the following can pass through 20 cm of steel?
A) Alpha particle
B) Beta particle
C) Gamma rays (Correct Answer)
D) None of the above
Explanation:
Gamma rays have the highest penetration among these radiations.
Q30 (2021 Exam)
1 Farad is equivalent to:
A) 1 C / 1 V (Correct Answer)
B) 1 V / 1 C
C) 19 / 1 C
D) None of the above
Explanation:
1 Farad = 1 Coulomb per Volt, the SI unit of capacitance.
Q31 (2021 Exam)
Rest mass energy of an electron is:
A) 511 eV
B) 51 keV
C) 0.511 MeV (Correct Answer)
D) None
Explanation:
The energy equivalent of electron mass is 0.511 MeV.
Q32 (2021 Exam)
X-rays can be deflected by:
A) Electric and magnetic fields (Correct Answer)
B) Only magnetic field
C) Only electric field
D) None
Explanation:
X-rays are uncharged; they are not deflected by fields — this checks understanding.
Q33 (2021 Exam)
Mean life (average life) of a radioactive element is:
A) 1.44 T½
B) 1.44 × half-life (Correct Answer)
C) 0.693 × T½
D) None
Explanation:
Mean life τ = 1.44 × T½ for exponential decay.
Q34 (2021 Exam)
Gamma radiation from Co-60 has energy:
A) 0.1 MeV
B) 1.17 & 1.33 MeV
C) Average 1.25 MeV (Correct Answer)
D) 2.0 MeV
Explanation:
Co-60 emits two γ-rays averaging 1.25 MeV.
Q35 (2021 Exam)
Which is not electromagnetic radiation?
A) X-rays
B) Alpha rays (Correct Answer)
C) Gamma rays
D) Light
Explanation:
Alpha rays are charged helium nuclei, not EM waves.
Q36 (2021 Exam)
Power factor in a purely capacitive circuit is:
A) 1
B) 0 (Correct Answer)
C) 10
D) None
Explanation:
Current leads voltage by 90°, hence real power = 0.
Q37 (2021 Exam)
Compton effect is due to interaction between:
A) Photon and free electron (Correct Answer)
B) Photon and nucleus
C) Photon and bound electron
D) None
Explanation:
Compton scattering involves interaction between a photon and a loosely bound (free) electron.
Q38 (2021 Exam)
An a-particle is emitted from Ra-226 nucleus. The daughter nucleus is:
A) Rn-222 (Correct Answer)
B) Po-210
C) Pb-210
D) Bi-214
Explanation:
Ra-226 → Rn-222 + α (reduces Z by 2, A by 4).
Q39 (2021 Exam)
The SI unit of dose equivalent is:
A) Gray
B) Sievert (Correct Answer)
C) Roentgen
D) Curie
Explanation:
Sievert measures biological effect; Gray measures absorbed dose.
Q40 (2021 Exam)
Type of equilibrium in Mo-99 and Tc-99m:
A) Secular
B) Transient (Correct Answer)
C) No equilibrium
D) None
Explanation:
Mo-99 and Tc-99m form a transient radioactive equilibrium.
Q41 (2021 Exam)
Threshold energy for pair production:
A) 0.511 MeV
B) 1.02 MeV (Correct Answer)
C) 2.04 MeV
D) None
Explanation:
Pair production requires at least 1.022 MeV (2 × 0.511 MeV).
Q42 (2021 Exam)
Unit of specific activity is:
A) Ci/hr
B) Bq/sec
C) Ci/gm (Correct Answer)
D) None
Explanation:
Specific activity = Activity per gram; unit is Ci/g or Bq/g.
Q43 (2021 Exam)
Type of radiation in Linear Accelerator:
A) Gamma rays
B) X-rays (Correct Answer)
C) Neutrons
D) Beta rays
Explanation:
A medical linear accelerator produces high-energy X-rays or electrons.
Q44 (2021 Exam)
Full form of REM is:
A) Roentgen Equivalent Man (Correct Answer)
B) Radiation Energy Measurement
C) Roentgen Electron Method
D) None
Explanation:
REM is an older unit for equivalent dose, replaced by Sievert.
Q45 (2021 Exam)
The unit of absorbed dose in SI system is:
A) Gray (Correct Answer)
B) Roentgen
C) Becquerel
D) REM
Explanation:
1 Gray = 1 joule of energy absorbed per kilogram of matter.
Here are Q46–Q70 (2020 Exam) from the DRT 1st Year Physics paper, formatted in the same clear layout:
Q46 (2020 Exam)
Cathode rays are:
A) Electromagnetic waves
B) Moving electrons (Correct Answer)
C) Moving negative ions
D) None of the above
Explanation:
Cathode rays are streams of electrons moving from cathode to anode in a discharge tube.
Q47 (2020 Exam)
Rest mass of electron is:
A) 930 MeV
B) 931 MeV
C) 0.511 MeV (Correct Answer)
D) None of the above
Explanation:
Rest energy of an electron is 0.511 MeV = 9.11×10⁻³¹ kg·c².
Q48 (2020 Exam)
In an electrical circuit an ammeter is connected in:
A) Parallel
B) Series (Correct Answer)
C) None of the above
D) Both of the above
Explanation:
An ammeter must be connected in series to measure the total circuit current.
Q49 (2020 Exam)
In ⁶⁰Co the mass number is:
A) 27
B) 33
C) 60 (Correct Answer)
D) 87
Explanation:
The isotope symbol ⁶⁰Co shows a mass number of 60.
Q50 (2020 Exam)
Unit of magnetic flux is:
A) Volt
B) Weber (Correct Answer)
C) Tesla
D) Curie
Explanation:
Weber is the SI unit for magnetic flux; 1 Wb = 1 T·m².
Q51 (2020 Exam)
Half-life of Ir-192 is:
A) 5.26 years
B) 14 days
C) 74 days (Correct Answer)
D) 30 years
Explanation:
Ir-192 has a half-life of about 74 days, used in brachytherapy.
Q52 (2020 Exam)
Circuit required to convert AC to DC:
A) Filter
B) Rectifier (Correct Answer)
C) Amplifier
D) None
Explanation:
A rectifier uses diodes to convert AC into DC.
Q53 (2020 Exam)
Source of radiation in Linear Accelerator:
A) X-rays
B) Electrons (Correct Answer)
C) Cs-137
D) Ir-192
Explanation:
A linac accelerates electrons to produce X-rays or electron beams.
Q54 (2020 Exam)
1 Roentgen equals:
A) 2.98 × 10⁻⁴ C/kg in air
B) 2.58 × 10⁻⁴ C/kg in air (Correct Answer)
C) 1 C/kg in air
D) None
Explanation:
1 R = 2.58 × 10⁻⁴ coulombs per kilogram of air ionized.
Q55 (2020 Exam)
Co-60 source in teletherapy machine is:
A) Accelerator produced
B) Reactor produced (Correct Answer)
C) None of the above
D) Both
Explanation:
Co-60 is made by neutron activation of Co-59 in a reactor.
Q56 (2020 Exam)
CaSO₄:Dy is used in:
A) Film Dosimetry
B) Thermoluminescent Dosimetry (Correct Answer)
C) Calorimetric Dosimetry
D) None
Explanation:
Calcium sulphate doped with dysprosium is a TLD phosphor material.
Q57 (2020 Exam)
X-rays consist of:
A) Charged particles
B) Uncharged electromagnetic radiation (Correct Answer)
C) None
Explanation:
X-rays are electromagnetic waves with no charge or mass.
Q58 (2020 Exam)
Threshold energy for pair production:
A) 1.02 MeV (Correct Answer)
B) 2.02 MeV
C) 0.511 MeV
D) 1.25 MeV
Explanation:
Pair production needs photon energy ≥ 1.022 MeV (2 × electron rest mass).
Q59 (2020 Exam)
1 Ci is equal to:
A) 2.7 × 10⁹ Bq
B) 3.7 × 10¹⁰ Bq (Correct Answer)
C) 3.7 × 10⁹ dps
D) 2.7 Bq
Explanation:
1 Curie = 3.7 × 10¹⁰ disintegrations per second.
Q60 (2020 Exam)
Compton interaction occurs between photon and:
A) Free electron (Correct Answer)
B) Bound electron
C) Proton
D) Nucleus
Explanation:
Compton scattering involves a photon colliding with a free or loosely bound electron.
Q61 (2020 Exam)
Half value layer of lead for Co-60 gamma ray is:
A) 1 cm
B) 1.2 cm (Correct Answer)
C) 0.5 cm
D) 2.0 cm
Explanation:
HVL for Co-60 in lead ≈ 1.2 cm.
Q62 (2020 Exam)
The unit of dose equivalent is:
A) Gray
B) Sievert (Correct Answer)
C) Roentgen
D) REM
Explanation:
Sievert measures biological dose equivalent in SI.
Q63 (2020 Exam)
Power factor in purely inductive circuit:
A) 1
B) 0 (Correct Answer)
C) 10
D) None
Explanation:
Power factor = 0 when voltage and current are 90° out of phase.
Q64 (2020 Exam)
Rest mass energy of an electron:
A) 511 eV
B) 51 keV
C) 0.511 MeV (Correct Answer)
D) 1 MeV
Explanation:
The electron rest mass energy equals 0.511 MeV.
Q65 (2020 Exam)
Type of radioactive equilibrium between Mo-99 and Tc-99m:
A) Secular
B) Transient (Correct Answer)
C) No equilibrium
D) None
Explanation:
Mo-99 and Tc-99m form a transient equilibrium.
Q66 (2020 Exam)
Threshold energy for pair production is:
A) 1.02 MeV (Correct Answer)
B) 0.511 MeV
C) 2.04 MeV
D) None
Explanation:
Pair production requires energy equal to twice the electron rest mass.
Q67 (2020 Exam)
Specific activity unit is:
A) Ci/hr
B) Bq/sec
C) Ci/g (Correct Answer)
D) None
Explanation:
Specific activity = activity per unit mass; expressed in Ci/g or Bq/g.
Q68 (2020 Exam)
Mean life of radioactive element is:
A) 1.44 T½
B) 1.44 × half-life (Correct Answer)
C) 0.693 × T½
D) None
Explanation:
Mean life τ = 1.44 × half-life (T½).
Q69 (2020 Exam)
Gamma rays from Co-60 have energy:
A) 0.1 MeV
B) 1.17 and 1.33 MeV
C) Average 1.25 MeV (Correct Answer)
D) 2.0 MeV
Explanation:
Co-60 emits two gamma rays averaging 1.25 MeV.
Q70 (2020 Exam)
Which of the following is not electromagnetic radiation?
A) X-rays
B) Alpha particles (Correct Answer)
C) Gamma rays
D) Light
Explanation:
Alpha particles are helium nuclei, not electromagnetic radiation.
Q71 (2019 Exam)
Which of the following wavelengths falls in the range of X-rays?
A) 0.1 Å
B) 100 nm
C) 1 Å (Correct Answer)
D) 1 cm
Explanation:
X-rays have wavelengths between about 0.01 and 10 Å.
Q72 (2019 Exam)
Unit of linear attenuation coefficient is:
A) cm
B) cm⁻¹ (Correct Answer)
C) cm²
D) none
Explanation:
The linear attenuation coefficient μ is expressed per unit length, typically cm⁻¹.
Q73 (2019 Exam)
LAMU stands for:
A) 6 MeV
B) 931 MeV
C) 1.6 × 10⁻¹³ J (Correct Answer)
Explanation:
1 atomic mass unit (1 amu) = 931 MeV = 1.66 × 10⁻²⁷ kg = 1.6 × 10⁻¹³ J.
Q74 (2019 Exam)
HVL of a monoenergetic beam is related to the linear attenuation coefficient μ as:
A) 0.693 / μ
B) HVL = 0.693 / μ (Correct Answer)
C) 1 / μ
D) μ / 0.693
Explanation:
HVL = 0.693 / μ is derived from I = I₀ e^(-μx).
Q75 (2019 Exam)
Frequency of A.C. mains in India is:
A) 100 Hz
B) 50 Hz (Correct Answer)
C) 230 Hz
D) 25 Hz
Explanation:
The standard frequency of alternating current in India is 50 Hz.
Q76 (2019 Exam)
Amount of original radioactive atoms left after 5 half-lives:
A) 3%
B) 3.125% (Correct Answer)
C) 5%
D) 10%
Explanation:
Remaining fraction = (½)⁵ = 1/32 = 3.125%.
Q77 (2019 Exam)
Heavy water is used in:
A) Nuclear reactor
B) Nuclear reactor (Correct Answer)
C) Cyclotron
D) Van de Graaff generator
Explanation:
Heavy water (D₂O) acts as a neutron moderator in reactors.
Q78 (2019 Exam)
Production of X-rays is a:
A) Nuclear phenomenon
B) Atomic phenomenon (Correct Answer)
C) Fission reaction
D) Fusion reaction
Explanation:
X-rays are generated by atomic electron transitions, not nuclear changes.
Q79 (2019 Exam)
25% of 80 is:
A) 30
B) 20 (Correct Answer)
C) 35
D) 25
Explanation:
25% × 80 = 20.
Q80 (2019 Exam)
What value of n will make the proportion 6 : 15 = n : 25?
A) 10 (Correct Answer)
B) 15
C) 18
D) 25
Explanation:
n = (6×25)/15 = 10.
Q81 (2019 Exam)
log(1×2×3) is equal to:
A) 0
B) log1 + log2 + log3 (Correct Answer)
C) log(1×2×3)
D) 1
Explanation:
log(ab) = loga + logb, so log(1×2×3) = log1 + log2 + log3.
Q82 (2019 Exam)
Auger electron is associated with:
A) Photoelectric effect (Correct Answer)
B) Compton effect
C) Pair production
D) None
Explanation:
Auger emission follows an inner-shell vacancy due to photoelectric absorption.
Q83 (2019 Exam)
In 5th generation CT:
A) X-ray source rotates alone
B) Detector rotates alone
C) Detector and X-ray source both rotate (Correct Answer)
D) None
Explanation:
Modern scanners rotate both source and detector arrays simultaneously.
Q84 (2019 Exam)
Which quantity is independent of density?
A) H
B) μ/ρ (mass attenuation coefficient) (Correct Answer)
C) ρ
D) μ
Explanation:
Mass attenuation coefficient μ/ρ is independent of material density.
Q85 (2019 Exam)
In an A.C. circuit, which statement is not true?
A) Current lags behind voltage in inductance
B) Voltage leads current in capacitor
C) Current leads voltage in resistance (Correct Answer)
Explanation:
In resistance, current and voltage are in phase, not leading or lagging.
Q86 (2019 Exam)
Annihilation reaction is associated with:
A) Compton scattering
B) Pair production (Correct Answer)
C) Photoelectric effect
D) None
Explanation:
In pair annihilation, an electron and positron convert into two gamma rays.
Q87 (2019 Exam)
Power factor in purely inductive circuit:
A) 1
B) 0 (Correct Answer)
C) 10
D) None
Explanation:
In pure inductance, current lags voltage by 90°, so power factor is zero.
Q88 (2019 Exam)
Relation between RMS voltage (Vᵣₘₛ) and peak voltage (Vₚ):
A) Vₚ = √2 × Vᵣₘₛ (Correct Answer)
B) Vₚ = Vᵣₘₛ/√2
C) Vₚ = 2 × Vᵣₘₛ
D) None
Explanation:
RMS voltage is the effective value; Vₚ = √2 × Vᵣₘₛ.
Q89 (2019 Exam)
Ground state energy of an electron in hydrogen atom is:
A) 13.6 eV
B) -13.6 eV (Correct Answer)
C) -13.6 keV
D) None
Explanation:
Ground state energy is negative (bound state) with value -13.6 eV.
Q90 (2019 Exam)
When a positive charged particle enters a magnetic field perpendicularly, it:
A) Moves unchanged
B) Describes a circular path (Correct Answer)
C) Moves in straight line
D) Spirals along field lines
Explanation:
The Lorentz force causes uniform circular motion perpendicular to the field.
Q91 (2019 Exam)
Neutrino is associated with:
A) Alpha emission
B) Beta emission (Correct Answer)
C) Gamma emission
D) None
Explanation:
Neutrinos are emitted during β decay to conserve energy and lepton number.
Q92 (2019 Exam)
Compton effect involves interaction between:
A) Photon and free electron (Correct Answer)
B) Photon and proton
C) Photon and nucleus
D) Two photons
Explanation:
Compton scattering occurs when a photon collides with a loosely bound electron.
Q93 (2019 Exam)
Half-value layer of lead for Co-60 gamma ray is:
A) 0.5 cm
B) 2.2 cm
C) 1.2 cm (Correct Answer)
D) 3.6 cm
Explanation:
HVL for Co-60 gamma in lead is approximately 1.2 cm.
Q94 (2019 Exam)
Rest mass energy of electron:
A) 511 eV
B) 51 keV
C) 0.511 MeV (Correct Answer)
D) 1.02 MeV
Explanation:
An electron at rest has energy 0.511 MeV = mₑc².
Q95 (2019 Exam)
The SI unit of dose equivalent is:
A) Gray
B) Sievert (Correct Answer)
C) Roentgen
D) REM
Explanation:
Sievert (Sv) represents equivalent dose including biological effectiveness.
Q96 (2018 Exam)
Unit of electric field is:
A) J/C²
B) N/C (Correct Answer)
C) V/m
Explanation:
Electric field intensity is measured in Newton per Coulomb (N/C), which equals volt per meter.
Q97 (2018 Exam)
1 Farad is equivalent to:
A) 1 C / 1 V (Correct Answer)
B) 1 V / 1 C
C) 19 / 1 C
Explanation:
Capacitance (Farad) = Charge (Coulomb) / Potential (Volt).
Q98 (2018 Exam)
An electric motor:
A) Generates mechanical energy
B) Converts mechanical energy into electrical energy
C) Converts electrical energy into mechanical energy (Correct Answer)
Explanation:
Electric motors convert electrical energy into mechanical work.
Q99 (2018 Exam)
Electromagnetic waves are:
A) Transverse and travel with same speed in all media
B) Transverse and travel at light speed in vacuum
C) Transverse and produced by accelerating charges (Correct Answer)
Explanation:
EM waves are generated by accelerating charges and propagate transversely.
Q100 (2018 Exam)
Electromagnetic rays are:
A) Cathode rays
B) Moving protons
C) X-rays (Correct Answer)
Explanation:
X-rays are electromagnetic waves with short wavelengths.
Q101 (2018 Exam)
Lowest energy photoelectrons are produced by:
A) Visible light
B) Ultraviolet rays (Correct Answer)
C) Gamma rays
Explanation:
Ultraviolet light has lower energy than gamma rays and produces lower energy electrons.
Q102 (2018 Exam)
In an X-ray tube, the quality of emitted X-ray increases by:
A) Increasing filament current
B) Increasing potential difference (Correct Answer)
C) Decreasing potential difference
Explanation:
Higher tube voltage increases photon energy and beam quality.
Q103 (2018 Exam)
β-rays emitted by a radioactive material are:
A) Electromagnetic waves
B) Charged particles emitted by nucleus (Correct Answer)
C) Orbiting electrons
Explanation:
Beta rays are high-speed electrons or positrons from nuclear decay.
Q104 (2018 Exam)
Which can pass through 20 cm of steel?
A) Alpha particle
B) Beta particle
C) Gamma rays (Correct Answer)
Explanation:
Gamma rays have the highest penetrating power among common radiations.
Q105 (2018 Exam)
An α-particle is emitted from Ra-226 nucleus. The daughter nucleus is:
A) Po-210
B) Rn-222 (Correct Answer)
C) Pb-210
Explanation:
Ra-226 → Rn-222 + α; atomic number decreases by 2, mass by 4.
Q106 (2018 Exam)
Half-life of a radioactive source:
A) Changes during decay
B) Remains constant (Correct Answer)
C) Depends on decay rate
Explanation:
Half-life is a characteristic constant of each radionuclide.
Q107 (2018 Exam)
Unit of specific activity is:
A) Ci/hr
B) Bq/sec
C) Ci/g (Correct Answer)
Explanation:
Specific activity measures activity per gram, given in Ci/g or Bq/g.
Q108 (2018 Exam)
Cathode rays are:
A) Electromagnetic waves
B) Streams of electrons (Correct Answer)
C) Positive ions
Explanation:
Cathode rays are high-speed electrons emitted from the cathode.
Q109 (2018 Exam)
Rest mass of electron is:
A) 931 MeV
B) 930 MeV
C) 0.511 MeV (Correct Answer)
Explanation:
The rest energy of an electron is 0.511 MeV = 9.11 × 10⁻³¹ kg·c².
Q110 (2018 Exam)
In an electrical circuit an ammeter is connected in:
A) Parallel
B) Series (Correct Answer)
C) None
Explanation:
Ammeter must be in series to measure total circuit current.
Q111 (2018 Exam)
In Co-60, the mass number is:
A) 27
B) 33
C) 60 (Correct Answer)
Explanation:
Co-60 has 27 protons and 33 neutrons, giving mass number 60.
Q112 (2018 Exam)
Unit of magnetic flux is:
A) Volt
B) Weber (Correct Answer)
C) Tesla
Explanation:
1 Weber = 1 Tesla·m²; the SI unit of magnetic flux.
Q113 (2018 Exam)
Half-life of Ir-192 is:
A) 14 days
B) 5.26 years
C) 74 days (Correct Answer)
Explanation:
Ir-192 decays with a half-life of about 74 days.
Q114 (2018 Exam)
Circuit required to convert AC to DC:
A) Filter
B) Rectifier (Correct Answer)
C) Amplifier
Explanation:
Rectifiers use diodes to convert alternating current to direct current.
Q115 (2018 Exam)
Wavelength of X-rays falls in range of:
A) 0.1 Å
B) 1 Å (Correct Answer)
C) 1 cm
Explanation:
X-ray wavelength range ≈ 0.01–10 Å.
Q116 (2018 Exam)
Power factor in purely inductive circuit:
A) 1
B) 0 (Correct Answer)
C) 10
Explanation:
Voltage leads current by 90°, so no real power (cosφ = 0).
Q117 (2018 Exam)
In 5th generation CT scanner:
A) X-ray source rotates alone
B) Detector rotates alone
C) Both rotate (Correct Answer)
Explanation:
In modern CT, both source and detector rotate for image acquisition.
Q118 (2018 Exam)
Electromagnetic rays include:
A) X-rays
B) Gamma rays
C) Both A and B (Correct Answer)
Explanation:
Both X-rays and gamma rays are forms of electromagnetic radiation.
Q119 (2018 Exam)
Photoelectric effect involves:
A) Photon and bound electron (Correct Answer)
B) Photon and nucleus
C) Two photons
Explanation:
A bound electron absorbs photon energy and is ejected.
Q120 (2018 Exam)
Co-60 emits gamma rays of energy:
A) 0.25 MeV
B) 1.17 and 1.33 MeV (Correct Answer)
C) 2.0 MeV
Explanation:
Cobalt-60 emits two γ-rays at 1.17 and 1.33 MeV (average 1.25 MeV).
Q121 (2017 Exam)
Compton effect is interaction of photons with:
A) Free electrons
B) Bound electrons
C) Protons (Correct Answer)
Explanation:
Compton scattering occurs when photons interact with loosely bound or free electrons.
Q122 (2017 Exam)
In a Ra-226 source the radioactive equilibrium that occurs is:
A) Secular equilibrium (Correct Answer)
B) Transient equilibrium
C) No equilibrium
Explanation:
Ra-226 and Rn-222 form a secular equilibrium due to their long half-lives.
Q123 (2017 Exam)
Half value layer of lead for Cs-137 gamma ray is:
A) 1.1 cm (Correct Answer)
B) 11.0 cm
C) 0.55 cm
Explanation:
HVL for Cs-137 gamma rays in lead ≈ 1.1 cm.
Q124 (2017 Exam)
In coherent scattering, the energy of the emitted photon is:
A) Equal to the incident photon (Correct Answer)
B) Equal to 1.02 MeV
C) 0.511 MeV
Explanation:
In coherent scattering, photon energy remains unchanged, only direction alters.
Q125 (2017 Exam)
Mean life of a radioactive source is:
A) τ = 1.44 T½ (Correct Answer)
B) τ = λ / 0.693
C) None of the above
Explanation:
Mean life (τ) = 1.44 × half-life (T½).
Q126 (2017 Exam)
Energy of EM radiation is given by:
A) E = hν (Correct Answer)
B) 1.24 × 10⁵
C) None
Explanation:
Energy is proportional to frequency; E = hν.
Q127 (2017 Exam)
Tenth value layer of lead for Co-60 gamma rays is:
A) 3.6 cm (Correct Answer)
B) 11.0 cm
C) 0.825 cm
Explanation:
TVL = 3.6 cm for Co-60 in lead, equal to 3.3 × HVL.
Q128 (2017 Exam)
Change that occurs during radioactive decay:
A) Half-life
B) Energy
C) Number of atoms (Correct Answer)
Explanation:
Radioactive decay reduces number of undecayed atoms exponentially.
Q129 (2017 Exam)
In fission:
A) A nucleus splits into nuclei of lower atomic number (Correct Answer)
B) Low mass nuclei combine
C) A nucleus splits into four nuclei
Explanation:
Fission involves the splitting of heavy nuclei into lighter ones.
Q130 (2017 Exam)
Unit of decay constant is:
A) cm²
B) sec⁻¹ (Correct Answer)
C) gram
Explanation:
Decay constant λ has units of inverse time (s⁻¹).
Q131 (2017 Exam)
Transformer converts:
A) Electrical to mechanical energy
B) Low voltage to high voltage (Correct Answer)
C) Heat to light
Explanation:
Transformers step up or down AC voltage.
Q132 (2017 Exam)
Total energy of electron in ground state of hydrogen atom is:
A) Zero
B) 13.6 eV
C) -13.6 eV (Correct Answer)
Explanation:
Bound electrons have negative total energy, equal to -13.6 eV in ground state.
Q133 (2017 Exam)
Electron emitted in beta radiation originates from:
A) Decay of neutron in nucleus (Correct Answer)
B) Outer orbit
C) Free electron
Explanation:
Beta particles are electrons from neutron-to-proton transformation.
Q134 (2017 Exam)
Atoms of same element differing in mass are called:
A) Isotopes (Correct Answer)
B) Isomers
C) Isobars
Explanation:
Isotopes have same atomic number but different mass numbers.
Q135 (2017 Exam)
In nuclear reaction, which quantities are conserved:
A) Energy and momentum (Correct Answer)
B) Mass only
C) None
Explanation:
In all nuclear reactions, energy, momentum, and charge are conserved.
Q136 (2017 Exam)
Tesla is the unit of:
A) Electric field
B) Magnetic field strength (Correct Answer)
C) Electromagnetic field
Explanation:
Tesla (T) is SI unit of magnetic flux density (B).
Q137 (2017 Exam)
Wavelength range of gamma rays is:
A) 10⁴–10⁷ m
B) 10⁰–10⁷ m
C) 10⁻¹⁰–10⁻¹² m (Correct Answer)
Explanation:
Gamma rays have the shortest wavelengths, around 10⁻¹⁰–10⁻¹² m.
Q138 (2017 Exam)
Penetrating power of X-rays increases with:
A) Wavelength
B) Frequency (Correct Answer)
C) Velocity
Explanation:
Shorter wavelength (higher frequency) = higher penetration.
Q139 (2017 Exam)
Decay of radioactive substance is:
A) Proportional
B) Inversely proportional
C) Exponential (Correct Answer)
Explanation:
Radioactive decay follows N = N₀e⁻ˡᵗ.
Q140 (2017 Exam)
Frequency of AC in India is:
A) 50 Hz (Correct Answer)
B) 60 Hz
C) 45 Hz
Explanation:
Indian power grid operates at 50 Hz.
Q141 (2017 Exam)
Energy of Co-60 gamma rays:
A) 0.25 MeV
B) 1.17 and 1.33 MeV (Correct Answer)
C) 2.0 MeV
Explanation:
Cobalt-60 emits two γ-rays averaging 1.25 MeV.
Q142 (2017 Exam)
Threshold energy for pair production:
A) 0.511 MeV
B) 1.02 MeV (Correct Answer)
C) 2.04 MeV
Explanation:
Two electron rest masses = 1.02 MeV minimum for pair production.
Q143 (2017 Exam)
Unit of dose equivalent is:
A) Gray
B) Sievert (Correct Answer)
C) Roentgen
Explanation:
Sievert (Sv) measures biological dose equivalent.
Q144 (2017 Exam)
Specific activity unit is:
A) Ci/hr
B) Bq/sec
C) Ci/g (Correct Answer)
Explanation:
Specific activity = Activity per gram of radionuclide.
Q145 (2017 Exam)
Compton interaction involves:
A) Photon and free electron (Correct Answer)
B) Photon and nucleus
C) Photon and positron
Explanation:
Compton scattering occurs with free or loosely bound electrons.
Q146 (2016 Exam)
The capacitance of a capacitor does not depend upon:
A) Size of the plates
B) Shape of the plates
C) Charge on the plates (Correct Answer)
Explanation:
Capacitance depends on plate area, distance, and dielectric but not on stored charge.
Q147 (2016 Exam)
An electric transformer:
A) Generates electricity
B) Converts mechanical energy into electrical energy
C) Converts low voltages into higher ones (Correct Answer)
Explanation:
Transformers step up or step down alternating voltage using mutual induction.
Q148 (2016 Exam)
Tesla is the unit of:
A) Magnetic flux density in SI system (Correct Answer)
B) Electric field intensity
C) Magnetic flux density in CGS system
Explanation:
1 Tesla = 1 Weber/m², SI unit of magnetic flux density.
Q149 (2016 Exam)
Which statement about electromagnetic waves is wrong?
A) Are transverse
B) Travel with same speed in all media (Correct Answer)
C) Are produced by accelerating charges
Explanation:
EM waves travel at light speed in vacuum, slower in other media.
Q150 (2016 Exam)
According to Bohr’s model, radius of stationary orbit is proportional to:
A) n
B) n³
C) n² (Correct Answer)
Explanation:
Bohr radius formula shows ( r_n ∝ n² ).
Q151 (2016 Exam)
Maximum energy of photoelectrons is independent of:
A) Frequency of incident light
B) Intensity of incident light (Correct Answer)
C) Nature of surface
Explanation:
Photoelectron energy depends on photon energy, not intensity.
Q152 (2016 Exam)
In an X-ray tube, intensity increases by:
A) Decreasing voltage
B) Increasing filament current (Correct Answer)
C) Increasing wavelength
Explanation:
More filament current emits more electrons, increasing X-ray output intensity.
Q153 (2016 Exam)
X-rays passing through magnetic field:
A) Deflected in direction of field
B) Deflected perpendicular
C) Not deflected at all (Correct Answer)
Explanation:
X-rays are uncharged EM waves, so they are unaffected by magnetic fields.
Q154 (2016 Exam)
Which of the following is not in helium atom?
A) 2 protons
B) 2 neutrons
C) 6 nucleons (Correct Answer)
Explanation:
Helium has 4 nucleons (2p + 2n).
Q155 (2016 Exam)
When ²³⁴Th emits β⁻ particle, resulting atom has:
A) Z=91, A=234 (Correct Answer)
B) Z=90, A=234
C) Z=98, A=230
Explanation:
β⁻ emission increases atomic number by 1 but leaves mass unchanged.
Q156 (2016 Exam)
Photoelectric effect shows:
A) Dependence on intensity
B) Dependence on frequency (Correct Answer)
C) Dependence on medium only
Explanation:
Photoelectric emission occurs only if photon frequency exceeds threshold.
Q157 (2016 Exam)
In an electrical circuit, voltmeter is connected:
A) Series
B) Parallel (Correct Answer)
C) None
Explanation:
A voltmeter is always connected across the component to measure voltage.
Q158 (2016 Exam)
SI unit of magnetic flux is:
A) Volt
B) Weber (Correct Answer)
C) Curie
Explanation:
Weber is unit for magnetic flux; 1 Wb = 1 T·m².
Q159 (2016 Exam)
The Co-60 source in teletherapy machine is:
A) Accelerator produced
B) Reactor produced (Correct Answer)
C) Both
Explanation:
Co-60 is formed by neutron activation of Co-59 in a nuclear reactor.
Q160 (2016 Exam)
Threshold energy for pair production is:
A) 0.511 MeV
B) 1.02 MeV (Correct Answer)
C) 2.04 MeV
Explanation:
Two electron rest masses (2 × 0.511 MeV) = 1.02 MeV.
Q161 (2016 Exam)
The unit of dose equivalent is:
A) Gray
B) Sievert (Correct Answer)
C) Roentgen
Explanation:
Sievert (Sv) accounts for radiation biological effect.
Q162 (2016 Exam)
Mean life of a radioactive isotope is:
A) 1.44 × Half-life (Correct Answer)
B) 0.693 × T½
C) λ × T½
Explanation:
τ = 1.44 × T½ is derived from exponential decay law.
Q163 (2016 Exam)
Gamma rays from Co-60 have average energy of:
A) 0.5 MeV
B) 2.0 MeV
C) 1.25 MeV (Correct Answer)
Explanation:
Co-60 emits 1.17 MeV and 1.33 MeV gamma rays (average 1.25 MeV).
Q164 (2016 Exam)
Power factor in purely capacitive circuit is:
A) 1
B) 0 (Correct Answer)
C) 10
Explanation:
Voltage lags current by 90°, so real power is zero.
Q165 (2016 Exam)
Rest mass energy of electron is:
A) 511 eV
B) 51 keV
C) 0.511 MeV (Correct Answer)
Explanation:
Rest energy E = mₑc² = 0.511 MeV.
Q166 (2016 Exam)
Photoelectric effect involves:
A) Photon and bound electron (Correct Answer)
B) Photon and nucleus
C) Two photons
Explanation:
Photon transfers energy to a bound electron which is ejected.
Q167 (2016 Exam)
Compton scattering involves:
A) Photon and free electron (Correct Answer)
B) Photon and proton
C) Photon and nucleus
Explanation:
Compton effect results from photon-electron collisions.
Q168 (2016 Exam)
Coherent scattering involves:
A) No energy loss, only direction change (Correct Answer)
B) Energy loss
C) Ionization
Explanation:
In coherent scattering, photon is deflected without energy change.
Q169 (2016 Exam)
Unit of specific activity is:
A) Ci/hr
B) Bq/sec
C) Ci/g (Correct Answer)
Explanation:
Specific activity = activity per unit mass.
Q170 (2016 Exam)
Half-life of Ir-192 is:
A) 14 days
B) 5.26 years
C) 74 days (Correct Answer)
Explanation:
Ir-192’s half-life is about 74 days, used in brachytherapy sources.
RTonc.site
Q171 (2015 Exam)
In current electricity, Ohm’s law is obeyed by all:
A) Solids
B) Metals (Correct Answer)
C) Gases
Explanation:
Ohm’s law applies well to metallic conductors under constant temperature.
Q172 (2015 Exam)
Gauss is the unit of:
A) Magnetic flux density in SI system
B) Electric field intensity
C) Magnetic flux density in CGS system (Correct Answer)
Explanation:
1 Gauss = 10⁻⁴ Tesla, used in the CGS system.
Q173 (2015 Exam)
An electric motor:
A) Generates mechanical energy
B) Converts mechanical energy into electrical energy
C) Converts electrical energy into mechanical energy (Correct Answer)
Explanation:
Electric motors convert electrical energy into rotational mechanical work.
Q174 (2015 Exam)
Electromagnetic waves:
A) Are transverse waves
B) Travel with speed of light in free space
C) Travel with same speed in all media (Correct Answer)
Explanation:
They travel at light speed in vacuum, but slower in matter.
Q175 (2015 Exam)
Cathode rays are:
A) Electromagnetic waves
B) Moving electrons (Correct Answer)
C) Moving negative ions
Explanation:
Cathode rays are streams of electrons emitted from cathode.
Q176 (2015 Exam)
Highest energy photoelectrons are produced by:
A) Visible light
B) Ultraviolet rays (Correct Answer)
C) X-rays
Explanation:
UV light has higher frequency and energy than visible light.
Q177 (2015 Exam)
In an X-ray tube, the intensity of emitted X-ray beam increases by:
A) Increasing filament current (Correct Answer)
B) Increasing potential difference
C) Decreasing potential difference
Explanation:
Higher filament current produces more electrons, raising X-ray intensity.
Q178 (2015 Exam)
Radioactive substances do not emit:
A) Electrons
B) Protons
C) Electromagnetic radiation (Correct Answer)
Explanation:
They emit α, β, and γ radiations — γ being electromagnetic; others are particles.
Q179 (2015 Exam)
Which particle does not exist in ²³⁸U nucleus?
A) 92 protons
B) 146 neutrons
C) 92 electrons (Correct Answer)
Explanation:
Electrons orbit outside the nucleus, not inside.
Q180 (2015 Exam)
An α-particle is emitted by the nucleus of ²²⁶Ra. The daughter nucleus has:
A) Z = 84, A = 224
B) Z = 86, A = 224
C) Z = 86, A = 222 (Correct Answer)
Explanation:
α-decay reduces atomic number by 2 and mass by 4.
Q181 (2015 Exam)
Transformer is not useful in:
A) Long-distance power transmission
B) Producing step-up DC voltage (Correct Answer)
C) Stepping up alternating voltage
Explanation:
Transformers only work with alternating current (AC), not DC.
Q182 (2015 Exam)
The total energy of an electron in ground state of hydrogen atom is:
A) Zero
B) 13.6 eV
C) -13.6 eV (Correct Answer)
Explanation:
Bound electrons have negative energy in ground state.
Q183 (2015 Exam)
The electron emitted in beta radiation originates from:
A) Inner orbits
B) Decay of neutron in nucleus (Correct Answer)
C) Free electrons
Explanation:
β⁻ emission converts neutron → proton + electron + antineutrino.
Q184 (2015 Exam)
Atoms of same element differing in mass are called:
A) Isotopes (Correct Answer)
B) Isomers
C) Isobars
Explanation:
Isotopes have same atomic number but different mass numbers.
Q185 (2015 Exam)
In nuclear reaction, the quantities conserved are:
A) Mass only
B) Energy and momentum (Correct Answer)
C) Charge only
Explanation:
Energy, momentum, and charge remain conserved in nuclear processes.
Q186 (2015 Exam)
Tesla is the unit of:
A) Electric field
B) Magnetic field strength (Correct Answer)
C) Electromagnetic field
Explanation:
1 Tesla = 1 Weber/m², SI unit for magnetic field.
Q187 (2015 Exam)
Wavelength range of gamma rays is:
A) 10⁴–10⁷ m
B) 10⁰–10⁷ m
C) 10⁻¹⁰–10⁻¹² m (Correct Answer)
Explanation:
Gamma rays have extremely short wavelengths (10⁻¹⁰–10⁻¹² m).
Q188 (2015 Exam)
Penetrating power of X-rays increases with:
A) Wavelength
B) Frequency (Correct Answer)
C) Velocity
Explanation:
Higher frequency (shorter wavelength) photons have higher energy and penetration.
Q189 (2015 Exam)
Decay of radioactive substances follows:
A) Proportional law
B) Inverse law
C) Exponential law (Correct Answer)
Explanation:
N = N₀e⁻ˡᵗ describes exponential decay.
Q190 (2015 Exam)
Frequency of AC in India is:
A) 50 Hz (Correct Answer)
B) 55 Hz
C) 45 Hz
Explanation:
Standard AC frequency in India is 50 hertz.
Q191 (2015 Exam)
A proton accelerated by 1 volt has kinetic energy:
A) 1/1840 eV
B) 1840 eV
C) 1 eV (Correct Answer)
Explanation:
Energy (eV) = Charge (e) × Potential (1 V) = 1 eV.
Q192 (2015 Exam)
Characteristic X-rays are emitted when:
A) Electrons are accelerated to a fixed energy
B) Source emits monoenergetic beam
C) Inner shell electron is knocked out and outer electron fills vacancy (Correct Answer)
Explanation:
Characteristic radiation occurs from inner shell transitions.
Q193 (2015 Exam)
Radioactive emission sequence in ²³⁹X → ²³⁴Y → ²¹⁴K is:
A) α, β, γ (Correct Answer)
B) β, α, γ
C) α, α, β
Explanation:
Alpha emission followed by beta, then gamma stabilization.
Q194 (2015 Exam)
For rectifying action we use:
A) Transformer
B) Condenser
C) Diode (Correct Answer)
Explanation:
Diodes allow unidirectional current, used for rectification.
Q195 (2015 Exam)
Radioactive decay law states that activity:
A) Decreases linearly with time
B) Decreases exponentially with time (Correct Answer)
C) Remains constant
Explanation:
Radioactive decay is exponential, not linear.
Q196 (2014 Exam)
Transformer is not useful in:
A) Long-distance power transmission
B) Producing step-up D.C. voltage
C) Stepping up alternating voltage
Answer: B) Producing step-up D.C. voltage
Explanation: Transformers work only with AC, not DC.
Q197 (2014 Exam)
Total energy of an electron in ground state of hydrogen atom is:
A) Zero
B) 13.6 eV
C) -13.6 eV
Answer: C) -13.6 eV
Explanation: Bound electrons have negative total energy.
Q198 (2014 Exam)
Electron emitted in beta radiation originates from:
A) Inner orbits of atom
B) Decay of neutron in nucleus
C) Free electrons existing in nuclei
Answer: B) Decay of neutron in nucleus
Explanation: Beta particle is emitted when a neutron decays into a proton and an electron.
Q199 (2014 Exam)
Atoms of an element differing in mass but same chemical properties are:
A) Isobars
B) Isomers
C) Isotopes
Answer: C) Isotopes
Explanation: Isotopes have same atomic number, different mass number.
Q200 (2014 Exam)
In nuclear reaction, conserved quantities are:
A) Mass only
B) Energy and momentum
C) All the three (mass, energy, charge)
Answer: C) All the three
Explanation: Energy, momentum, and charge remain conserved in nuclear reactions.
Q201 (2014 Exam)
Tesla is the unit of:
A) Electric field strength
B) Magnetic field strength
C) Electromagnetic field
Answer: B) Magnetic field strength
Explanation: Tesla is SI unit for magnetic flux density (B).
Q202 (2014 Exam)
Wavelength range of Gamma Rays:
A) 10⁴–10⁷ m
B) 10⁰–10⁷ m
C) 10⁻¹⁰–10⁻¹² m
Answer: C) 10⁻¹⁰–10⁻¹² m
Explanation: Gamma rays have very short wavelengths and high frequency.
Q203 (2014 Exam)
Penetrating power of X-rays increases with:
A) Wavelength
B) Frequency
C) Velocity
Answer: B) Frequency
Explanation: Shorter wavelength (higher frequency) means higher energy photons.
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Q204 (2014 Exam)
Decay of radioactive substances is:
A) Proportional
B) Inversely proportional
C) Exponential
Answer: C) Exponential
Explanation: Follows N = N₀e⁻ˡᵗ, an exponential decay law.
Q205 (2014 Exam)
Frequency of AC in India:
A) 50 Hz
B) 55 Hz
C) 45 Hz
Answer: A) 50 Hz
Explanation: Indian mains frequency standard is 50 cycles per second.
Q206 (2014 Exam)
In current electricity, Ohm’s law is obeyed by all:
A) Solids
B) Metals
C) Gases
Answer: B) Metals
Explanation: Ohm’s law holds for metallic conductors under constant temperature.
Q207 (2014 Exam)
Gauss is the unit of:
A) Magnetic flux density in SI system
B) Electric field intensity
C) Magnetic flux density in CGS system
Answer: C) Magnetic flux density in CGS system
Explanation: 1 Gauss = 10⁻⁴ Tesla.
Q208 (2014 Exam)
An electric motor:
A) Generates mechanical energy
B) Converts mechanical energy into electrical energy
C) Converts electrical energy into mechanical energy
Answer: C) Converts electrical energy into mechanical energy
Explanation: Converts electrical energy to motion.
Q209 (2014 Exam)
Point out the wrong statement: Electromagnetic waves:
A) Are transverse waves
B) Travel with speed of light in free space
C) Travel with same speed in all media
Answer: C) Travel with same speed in all media
Explanation: EM waves travel slower in media than in vacuum.
Q210 (2014 Exam)
Cathode rays are:
A) Electromagnetic waves
B) Moving electrons
C) Moving negative ions
Answer: B) Moving electrons
Explanation: Cathode rays are streams of electrons.
Q211 (2014 Exam)
Highest energy photoelectrons are produced by:
A) Visible light
B) Ultraviolet rays
C) X-rays
Answer: B) Ultraviolet rays
Explanation: UV photons have higher energy than visible light photons.
Q212 (2014 Exam)
In an X-ray tube, the intensity of emitted X-ray beam increases by:
A) Increasing filament current
B) Increasing potential difference
C) Decreasing potential difference
Answer: A) Increasing filament current
Explanation: More filament current → more electrons → higher intensity.
Q213 (2014 Exam)
Radioactive substances do not emit:
A) Electrons
B) Protons
C) Electromagnetic radiation
Answer: C) Electromagnetic radiation
Explanation: They emit α, β, and γ rays; γ is EM but β and α are particles.
Q214 (2014 Exam)
Which particle does not exist in ²³⁸U nucleus?
A) 92 protons
B) 92 electrons
C) 146 neutrons
Answer: B) 92 electrons
Explanation: Electrons are outside the nucleus.
Q215 (2014 Exam)
When an α-particle is emitted by the nucleus of radium (²²⁶Ra), the daughter nucleus has:
A) Z = 84, A = 224
B) Z = 86, A = 224
C) Z = 86, A = 222
Answer: C) Z = 86, A = 222
Explanation: α decay reduces atomic number by 2 and mass by 4.
Q216 (2014 Exam)
Transformer is used for:
A) Producing DC current
B) Stepping up or stepping down AC voltage
C) Storing electrical energy
Answer: B) Stepping up or stepping down AC voltage
Explanation: Transformers modify AC voltage levels.
RTonc.site
Q217 (2014 Exam)
The mean life of a radioactive source (Tₐ):
A) = 1.44 × half-life
B) = 0.693 × half-life
C) = 1/λ
Answer: A) = 1.44 × half-life
Explanation: Mean life is related to half-life by Tₐ = 1.44 × T½.
Q218 (2014 Exam)
Compton effect involves:
A) Elastic collision between photon and free electron
B) Photon absorption without scattering
C) Pair production
Answer: A) Elastic collision between photon and free electron
Explanation: Photon transfers part of its energy to an electron.
Q219 (2014 Exam)
Half-value layer (HVL) is defined as:
A) Thickness reducing radiation intensity to half
B) Energy of emitted photon
C) Thickness where intensity doubles
Answer: A) Thickness reducing radiation intensity to half
Explanation: HVL is a measure of beam attenuation.
Q220 (2014 Exam)
Frequency of AC in India is:
A) 45 Hz
B) 50 Hz
C) 60 Hz
Answer: B) 50 Hz
Explanation: Standard power frequency is 50 Hz across India.
Q221 (2013 Exam)
A proton is accelerated from rest through a potential difference of one volt. Its kinetic energy will be:
A) 1/1840 eV
B) 1840 eV
C) 1 eV (Correct Answer)
Explanation: A 1-volt acceleration gives a proton kinetic energy equal to 1 eV.
Q222 (2013 Exam)
The characteristic X-ray is emitted when:
A) Electrons are accelerated to a fixed energy
B) Source emits monoenergetic beam
C) Inner-shell electron is knocked out and outer electron fills the vacancy (Correct Answer)
Explanation: The characteristic X-ray is produced by inner-shell transitions.
Q223 (2013 Exam)
In the reaction ²³⁹X → ²³⁴Y → ²¹⁴K → ²¹⁴K, radioactive radiations are emitted in the following sequence:*
A) α, β, γ (Correct Answer)
B) β, α, γ
C) α, α, β
Explanation: Alpha emission reduces Z and A; beta restores Z; gamma stabilizes the nucleus.
Q224 (2013 Exam)
A radioactive substance has a half-life of four months. 3/4ths of the substance will decay in:
A) 3 months
B) 8 months
C) 12 months (Correct Answer)
Explanation: After two half-lives (8 months), 3/4th decays; the process completes within roughly that duration.
Q225 (2013 Exam)
For rectifying action we use:
A) Transformer
B) Condenser
C) Diode (Correct Answer)
Explanation: Diodes allow unidirectional current, converting AC to DC.
Q226 (2013 Exam)
Direction of motion of a current-carrying conductor in magnetic field is given by:
A) Fleming’s Left-Hand Rule (Correct Answer)
B) Fleming’s Right-Hand Rule
C) Lenz’s Law
Explanation: Fleming’s Left-Hand Rule gives direction of force on a current in a magnetic field.
Q227 (2013 Exam)
According to the radioactive decay law, activity:
A) Decreases linearly with time
B) Increases exponentially with time
C) Decreases exponentially with time (Correct Answer)
Explanation: Radioactive decay follows N = N₀e⁻ˡᵗ, showing exponential fall.
Q228 (2013 Exam)
Wavelength of electromagnetic wave is proportional to:
A) Frequency
B) Intensity
C) 1/Frequency (Correct Answer)
Explanation: λ = c/f, hence inversely proportional to frequency.
Q229 (2013 Exam)
In an X-ray tube, most of the energy of electrons is converted into:
A) Heat (Correct Answer)
B) X-rays
C) Light
Explanation: More than 99% of energy is lost as heat; < 1% becomes X-rays.
Q230 (2013 Exam)
Cathode rays are:
A) Electromagnetic waves
B) Streams of electrons (Correct Answer)
C) Negative ions
Explanation: Cathode rays consist of high-speed electrons emitted from cathode.
Q231 (2013 Exam)
Radioactive decay law states that activity:
A) Increases with time
B) Remains constant
C) Decreases exponentially with time (Correct Answer)
Explanation: Activity follows the exponential law (A = A_0 e^{-λt}).
Q232 (2013 Exam)
Wavelength of electromagnetic waves is proportional to:
A) Frequency
B) Intensity
C) 1/Frequency (Correct Answer)
Explanation: (λ = c/f); thus, it’s inversely proportional to frequency.
Q233 (2013 Exam)
In an X-ray tube, most of the electron energy is converted to:
A) Heat (Correct Answer)
B) X-rays
C) Light
Explanation: More than 99% of the energy converts to heat at the anode.
Q234 (2013 Exam)
Cathode rays are:
A) Electromagnetic waves
B) Streams of electrons (Correct Answer)
C) Negative ions
Explanation: Cathode rays are electrons emitted from cathode under high voltage.
Q235 (2013 Exam)
The kinetic energy of a proton accelerated by 1 volt is:
A) 1 eV (Correct Answer)
B) 1840 eV
C) 1/1840 eV
Explanation: (E = qV = 1e × 1V = 1 eV).
Q236 (2013 Exam)
The characteristic X-rays are produced when:
A) Outer electrons accelerate to high energy
B) Source emits uniform energy beam
C) Inner-shell electron is knocked out and outer one fills the vacancy (Correct Answer)
Explanation: Inner-shell transition releases characteristic X-rays.
Q237 (2013 Exam)
For rectification purpose we use:
A) Transformer
B) Condenser
C) Diode (Correct Answer)
Explanation: Diodes allow current to flow in one direction only.
Q238 (2013 Exam)
A radioactive substance having half-life of 4 months — 3/4th of it will decay in:
A) 3 months
B) 8 months (Correct Answer)
C) 12 months
Explanation: Two half-lives (8 months) result in 3/4th decay.
Q239 (2013 Exam)
The sequence of radiations in ²³⁹X → ²³⁴Y → ²¹⁴K → ²¹⁴K*
A) α, β, γ (Correct Answer)
B) β, α, γ
C) α, α, β
Explanation: Alpha decay reduces Z and A; beta restores charge; gamma stabilizes.
Q240 (2013 Exam)
Rest mass of electron is:
A) 931 MeV
B) 930 MeV
C) 0.511 MeV (Correct Answer)
Explanation: The electron rest mass corresponds to 0.511 MeV energy equivalent.
Q241 (2013 Exam)
1 Curie (Ci) is equal to:
A) 1 Bq
B) 3.7 × 10¹⁰ Bq (Correct Answer)
C) 2.7 × 10⁹ Bq
Explanation: 1 Ci corresponds to 3.7 × 10¹⁰ disintegrations per second.
Q242 (2013 Exam)
In an electrical circuit, an ammeter is connected in:
A) Parallel
B) Series (Correct Answer)
C) Both
Explanation: An ammeter measures current and must be in series.
Q243 (2013 Exam)
Half-life of Iridium-192 is:
A) 14 days
B) 74 days (Correct Answer)
C) 5.26 years
Explanation: The half-life of Ir-192 is approximately 74 days.
Q244 (2013 Exam)
The Co-60 source used in teletherapy machine is:
A) Accelerator-produced
B) Reactor-produced (Correct Answer)
C) Cyclotron-produced
Explanation: Co-60 is manufactured in nuclear reactors by neutron activation.
Q245 (2013 Exam)
Which of the following can pass through 20 cm of steel?
A) Alpha particles
B) Beta particles
C) Gamma rays (Correct Answer)
Explanation: Gamma rays have high penetration power compared to α and β particles.
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