NEET Physics: Modern Physics MCQ Questions for Quick Revision (2025)

Description:

Boost your NEET 2025 preparation with our curated collection of Modern Physics MCQ questions. This quick revision guide is designed for NEET aspirants looking to strengthen their grasp on Modern Physics concepts. Practice high-yield, frequently asked questions covering topics like Photoelectric Effect, Nuclear Physics, Dual Nature of Matter, and more. Perfect for last-minute revision and time-bound practice.

Keywords: NEET Physics 2025, Modern Physics MCQs, NEET MCQ questions, NEET quick revision, Physics practice questions, NEET 2025 preparation, Modern Physics NEET questions, last-minute NEET revision, important NEET Physics topics

NEET Physics: Modern Physics MCQ Questions for Quick Revision (2025)

Looking to strengthen your Modern Physics concepts for NEET 2025? Here's a carefully curated list of Modern Physics MCQ questions tailored for NEET 2025 quick revision. These questions cover all the essential topics including photoelectric effect, Bohr’s model, nuclear physics, radioactivity, and more. Ideal for last-minute revision, these questions will help boost your NEET Physics score.

📘 NEET Modern Physics Important Topics

Before diving into the MCQs, here are the must-revise topics from Modern Physics for NEET 2025:

Photoelectric Effect
Dual Nature of Matter and Radiation
Atomic Models (Bohr’s Theory)
X-rays
Nuclear Physics: Radioactivity, Binding Energy
Semiconductors (Basics)

✅ Modern Physics MCQ Questions for NEET 2025

1. The energy of a photon is 3.3 × 10⁻¹⁹ J. What is its frequency? (Planck's constant h = 6.6 × 10⁻³⁴ J·s)

A. 5 × 10¹⁴ Hz
B. 1 × 10¹⁵ Hz
C. 2 × 10¹⁵ Hz
D. 3 × 10¹³ Hz
Answer: A

2. In the photoelectric effect, increasing the intensity of incident light increases:

A. Threshold frequency
B. Kinetic energy of electrons
C. Number of photoelectrons emitted
D. Work function of the material
Answer: C

3. The de Broglie wavelength of an electron accelerated by a potential difference of 100 V is approximately:

A. 0.122 nm
B. 0.388 nm
C. 1.23 nm
D. 3.66 nm
Answer: A

4. According to Bohr’s model, the angular momentum of an electron in the nth orbit is proportional to:

A. √n
B. n²
C. n
D. 1/n
Answer: C

5. A radioactive substance has a half-life of 10 days. After 30 days, the fraction of the substance remaining is:

A. 1/2
B. 1/4
C. 1/8
D. 1/16
Answer: C

6. The energy released in the nuclear fission of one uranium-235 atom is approximately:

A. 1 eV
B. 200 eV
C. 200 MeV
D. 2 MeV
Answer: C

7. The minimum energy required to remove an electron from the metal surface is known as:

A. Kinetic energy
B. Work function
C. Ionization energy
D. Threshold energy
Answer: B

8. X-rays are produced when:

A. Electrons are accelerated in a magnetic field
B. Electrons hit the target in an X-ray tube
C. Nuclei undergo fission
D. Light hits a metal surface
Answer: B

9. The binding energy per nucleon is maximum for:

A. Uranium
B. Deuterium
C. Iron
D. Helium
Answer: C

10. The stopping potential in a photoelectric experiment is directly proportional to:

A. Intensity of light
B. Wavelength of light
C. Frequency of incident radiation
D. Work function
Answer: C

✅ Continued: Modern Physics MCQ Questions for NEET 2025

11. Which of the following has the shortest de Broglie wavelength, assuming same kinetic energy?

A. Proton
B. Electron
C. Neutron
D. Alpha particle
Answer: D
📝 Heavier particles have shorter de Broglie wavelengths at the same kinetic energy.

12. Which spectral line in the hydrogen atom corresponds to the transition from n = 4 to n = 2?

A. Lyman series
B. Balmer series
C. Paschen series
D. Brackett series
Answer: B

13. Which physical quantity remains conserved in both nuclear fission and fusion?

A. Mass
B. Energy
C. Number of protons
D. Binding energy
Answer: B

14. The correct expression for the energy of an electron in the nth orbit of hydrogen atom is:

A. $E_n = -13.6n \, \text{eV}$
B. $E_n = -\frac{13.6}{n^2} \, \text{eV}$
C. $E_n = -13.6 \cdot n^2 \, \text{eV}$
D. $E_n = 13.6n^2 \, \text{eV}$
Answer: B

15. A certain radioactive element decays such that 75% of the sample disappears in 2 hours. What is the half-life?

A. 30 minutes
B. 1 hour
C. 2 hours
D. 4 hours
Answer: B
📝 75% decay → 2 half-lives → Half-life = 2 hours ÷ 2 = 1 hour

16. In a nuclear reaction, the total mass of products is less than the total mass of reactants. This difference is called:

A. Binding energy
B. Mass defect
C. Ionization loss
D. Disintegration energy
Answer: B

17. The maximum kinetic energy of photoelectrons emitted depends on:

A. Intensity of light
B. Frequency of light
C. Number of photons
D. Temperature of the metal
Answer: B

18. The rest mass energy of an electron is approximately:

A. 13.6 eV
B. 1.6 × 10⁻¹⁹ J
C. 0.511 MeV
D. 9.1 × 10⁻³¹ kg
Answer: C

19. A sample has activity of 1000 Bq. After 2 half-lives, what will be the remaining activity?

A. 500 Bq
B. 250 Bq
C. 125 Bq
D. 100 Bq
Answer: B

20. Which of the following statements about Bohr’s atomic model is incorrect?

A. Electrons revolve in circular orbits without radiating energy
B. Energy levels are quantized
C. Angular momentum is an integral multiple of $\hbar$
D. It explains the spectra of all elements
Answer: D

✅ More NEET 2025: Modern Physics MCQ Questions for Practice

21. Which of the following particles will have the highest velocity if all have the same de Broglie wavelength?

A. Electron
B. Proton
C. Alpha particle
D. Neutron
Answer: A
📝 At the same de Broglie wavelength, lighter particles have higher velocity.

22. The unit of radioactive decay constant (λ) is:

A. Second
B. Becquerel
C. s⁻¹
D. m/s
Answer: C

23. Which of the following is not a characteristic of nuclear force?

A. Short-range
B. Charge-independent
C. Stronger than electromagnetic force
D. Inversely proportional to distance squared
Answer: D
📝 Nuclear force does not follow an inverse-square law like electrostatics or gravity.

24. Which radiation is most penetrating in matter?

A. Alpha
B. Beta
C. Gamma
D. Neutron
Answer: C

25. The time in which a radioactive substance reduces to 1/16th of its original amount is:

A. 2 half-lives
B. 3 half-lives
C. 4 half-lives
D. 5 half-lives
Answer: C
📝 $(1/2)^4 = 1/16$ , so 4 half-lives.

26. What is the change in atomic number and mass number when a nucleus emits a beta⁻ particle?

A. Atomic number increases by 1, mass number unchanged
B. Atomic number decreases by 1, mass number unchanged
C. Atomic number unchanged, mass number decreases by 1
D. Atomic number increases by 1, mass number increases by 1
Answer: A

27. The process of pair production can occur if the photon energy is at least:

A. 0.511 MeV
B. 1.022 MeV
C. 1.5 MeV
D. 2 MeV
Answer: B
📝 1.022 MeV = 2 × 0.511 MeV (mass energy of electron + positron).

28. If the frequency of incident light is below the threshold frequency, what will happen in the photoelectric effect?

A. Photoelectrons are emitted with lesser velocity
B. Photoelectrons are emitted with zero velocity
C. No photoelectrons are emitted
D. Emission continues due to intensity
Answer: C

29. In Bohr's model of hydrogen atom, the radius of the nth orbit is proportional to:

A. n
B. n²
C. 1/n
D. √n
Answer: B

30. The number of neutrons in an alpha particle is:

A. 0
B. 2
C. 4
D. 1
Answer: B
📝 Alpha particle = He²⁺ = 2 protons + 2 neutrons.

✅ Advanced NEET 2025: Modern Physics MCQ Questions (Set 4)

31. Which isotope is used in radiocarbon dating?

A. C-12
B. C-14
C. U-238
D. Co-60
Answer: B
📝 Carbon-14 is used to determine the age of archaeological samples.

32. A nucleus with atomic number Z and mass number A emits an alpha particle. The new nucleus has:

A. Z – 2, A – 2
B. Z – 4, A – 2
C. Z – 2, A – 4
D. Z – 4, A – 4
Answer: C
📝 Alpha particle emission decreases atomic number by 2 and mass number by 4.

33. The mass defect of a nucleus is directly related to its:

A. Binding energy
B. Ionization energy
C. Nuclear volume
D. Atomic number
Answer: A

34. Which of the following best explains the stability of the nucleus?

A. Neutron-proton ratio
B. Nuclear charge
C. Mass number
D. Electron configuration
Answer: A

35. The relation between binding energy (BE) and mass defect (Δm) is:

A. $\text{BE} = \frac{Δm}{c^2}$
B. $\text{BE} = Δm \times c^2$
C. $\text{BE} = Δm \times g$
D. $\text{BE} = \frac{Δm}{h}$
Answer: B

36. The number of electrons in the first Bohr orbit of hydrogen is:

A. 0
B. 1
C. 2
D. 4
Answer: B

37. If the half-life of a radioactive element is 5 days, how much of a 20g sample will remain after 15 days?

A. 10 g
B. 5 g
C. 2.5 g
D. 1.25 g
Answer: D
📝 After 3 half-lives: $20 \rightarrow 10 \rightarrow 5 \rightarrow 2.5 \rightarrow 1.25$ g

38. The stopping potential in a photoelectric experiment is zero when:

A. Frequency < threshold frequency
B. Intensity is zero
C. Metal is heated
D. Frequency > threshold frequency
Answer: A

39. The wave nature of electrons is confirmed by:

A. Photoelectric effect
B. Hydrogen spectrum
C. X-ray production
D. Davisson-Germer experiment
Answer: D

40. In photoelectric emission, the energy of the ejected electron increases with:

A. Decreasing intensity
B. Increasing frequency
C. Decreasing frequency
D. Increasing work function
Answer: B

✅ NEET 2025 Modern Physics MCQ Questions (Set 5)

41. The number of photons emitted per second by a monochromatic light source of power 1 W and wavelength 500 nm is approximately:

(Take $h = 6.63 \times 10^{-34} \, \text{J·s}$ , $c = 3 \times 10^8 \, \text{m/s}$ )

A. $1.5 \times 10^{18}$
B. $2.5 \times 10^{19}$
C. $4.0 \times 10^{20}$
D. $5.0 \times 10^{16}$
Answer: B
📝 Energy per photon = $E = \frac{hc}{\lambda}$ ; divide power by energy per photon.

42. In a hydrogen atom, the wavelength of radiation emitted during the transition from n = 3 to n = 2 is called:

A. Lyman-alpha line
B. Balmer-alpha line
C. Paschen-beta line
D. Brackett-alpha line
Answer: B

**43. Which quantity does not change during a nuclear reaction?**

A. Mass
B. Atomic number
C. Total energy
D. Nucleon number of individual atoms
Answer: C
📝 Energy is conserved even if mass is converted to energy.

44. A sample initially contains 80 g of a radioactive material. After 2 hours, only 10 g remains. What is its half-life?

A. 30 minutes
B. 1 hour
C. 40 minutes
D. 20 minutes
Answer: A
📝 80 → 40 → 20 → 10; 3 half-lives in 2 hours → Half-life = 40 minutes = 2 hours / 3.

45. X-rays are produced when:

A. Electrons move between atomic energy levels
B. Inner-shell electrons are ionized and outer electrons drop to fill the vacancy
C. High-energy electrons strike a metal target
D. Gamma rays strike a fluorescent screen
Answer: C

46. What happens to the wavelength of emitted radiation as an electron jumps from n = 4 to n = 2 compared to n = 3 to n = 2 in hydrogen atom?

A. It increases
B. It decreases
C. Remains same
D. Becomes zero
Answer: B
📝 Greater energy difference = shorter wavelength.

47. What is the effect of increasing the frequency of light beyond the threshold frequency in photoelectric effect?

A. Increases number of electrons emitted
B. Decreases stopping potential
C. Increases kinetic energy of photoelectrons
D. No effect
Answer: C

48. A radioactive isotope has a decay constant of $0.001 \, \text{s}^{-1}$ . What is its half-life?

A. 100 s
B. 693 s
C. 693 ms
D. 0.693 s
Answer: B
📝 $T_{1/2} = \frac{0.693}{λ} = \frac{0.693}{0.001} = 693 \, \text{s}$

49. Which experiment proved the wave nature of electrons?

A. Michelson-Morley experiment
B. Millikan’s oil drop experiment
C. Davisson and Germer experiment
D. Rutherford’s alpha scattering experiment
Answer: C

50. Which one of the following statements is true about gamma radiation?

A. It has charge +1
B. It is deflected by electric field
C. It has the highest ionizing power
D. It has the highest penetrating power
Answer: D

✅ NEET 2025 Modern Physics MCQ Questions (Set 6)

51. If the energy of an electron in the second orbit of hydrogen atom is -3.4 eV, what is the energy in the fourth orbit?

A. -6.8 eV
B. -1.7 eV
C. -13.6 eV
D. -0.85 eV
Answer: D
📝 Use $E_n = \frac{-13.6}{n^2}$ → $E_4 = \frac{-13.6}{16} = -0.85 \, \text{eV}$

52. The kinetic energy of a photoelectron depends on:

A. Wavelength of light
B. Intensity of light
C. Work function of metal
D. Both A and C
Answer: D
📝 Photoelectric equation: $K.E. = \frac{hc}{\lambda} - \phi$

53. A sample undergoes 3 half-lives. What percentage of the original nuclei remain?

A. 87.5%
B. 25%
C. 12.5%
D. 6.25%
Answer: C
📝 Remaining = $(1/2)^3 = 1/8 = 12.5\%$

54. The energy released when an electron jumps from n = 5 to n = 1 in a hydrogen atom will be:

A. More than n = 5 to n = 2
B. Less than n = 5 to n = 2
C. Same as n = 2 to n = 1
D. Cannot be predicted
Answer: A
📝 Greater energy difference → higher energy photon emitted

55. The photoelectric effect supports which theory of light?

A. Wave theory
B. Newton’s corpuscular theory
C. Quantum theory
D. Diffraction theory
Answer: C

56. When a β⁻ particle is emitted:

A. A neutron converts into a proton
B. A proton converts into a neutron
C. Mass number increases by 1
D. Atomic number decreases by 1
Answer: A

57. If the de Broglie wavelength of a particle is 0.02 nm, and its momentum is p, what is its mass if speed v = 3 × 10⁵ m/s?

Use $h = 6.63 \times 10^{-34}$ J·s
A. $1.1 \times 10^{-27} \, \text{kg}$
B. $2.2 \times 10^{-27} \, \text{kg}$
C. $3.3 \times 10^{-30} \, \text{kg}$
D. $1.1 \times 10^{-30} \, \text{kg}$
Answer: A
📝 Use $\lambda = \frac{h}{mv} \Rightarrow m = \frac{h}{\lambda v}$

58. Which of the following is true regarding alpha decay?

A. Occurs in light nuclei
B. Atomic number decreases by 4
C. Mass number decreases by 2
D. Nucleus becomes more stable
Answer: D

59. Gamma radiation differs from X-rays mainly in:

A. Speed
B. Charge
C. Origin
D. Wavelength
Answer: C
📝 Gamma rays come from nucleus; X-rays from electron transitions.

60. If 75% of a radioactive substance decays in 6 hours, its half-life is:

A. 3 h
B. 4 h
C. 2 h
D. 6 h
Answer: C
📝 75% decayed → 25% remains → (1/4 = 1/2²) → 2 half-lives → Half-life = 6/2 = 3 h

✅ NEET 2025 Modern Physics MCQ Questions (Set 7)

61. Which of the following transitions in the hydrogen atom emits radiation with the highest frequency?

A. n = 3 → n = 2
B. n = 4 → n = 3
C. n = 5 → n = 1
D. n = 2 → n = 1
Answer: C
📝 Larger energy difference = higher frequency.

62. In the Davisson-Germer experiment, electron diffraction confirmed:

A. Dual nature of light
B. Dual nature of matter
C. Nuclear model of atom
D. Uncertainty principle
Answer: B

63. A sample has a half-life of 1 hour. How much of the original sample remains undecayed after 5 hours?

A. 6.25%
B. 12.5%
C. 3.125%
D. 25%
Answer: C
📝 After 5 half-lives → $\left(\frac{1}{2}\right)^5 = \frac{1}{32} = 3.125\%$

64. The mass number of a nucleus changes when it emits:

A. Beta particle
B. Gamma ray
C. Alpha particle
D. Positron
Answer: C
📝 Alpha particle = 2 protons + 2 neutrons → mass number decreases by 4.

65. Which of the following has the maximum penetrating power?

A. Alpha rays
B. Beta rays
C. Gamma rays
D. X-rays
Answer: C

66. What is the order of energy of visible photons?

A. ~10⁻²⁰ J
B. ~10⁻¹⁷ J
C. ~10⁻¹⁹ J
D. ~10⁻²¹ J
Answer: C
📝 Visible light photon energy typically ranges from 1.5–3.1 eV = ~10⁻¹⁹ J

67. When an electron falls from n = 5 to n = 2, the emitted photon lies in which region?

A. Infrared
B. Ultraviolet
C. Visible
D. X-ray
Answer: C
📝 This transition is part of the Balmer series, which lies in the visible range.

68. What is the dimension of Planck’s constant (h)?

A. ML²T⁻²
B. ML²T⁻¹
C. MLT⁻²
D. MLT⁻¹
Answer: B
📝 From $E = h\nu$ → $[h] = [E]/[\nu] = ML²T⁻² / T⁻¹ = ML²T⁻¹$

69. A photon has energy 3 eV. What is its wavelength?

(Use $h = 6.63 \times 10^{-34} \, \text{J·s}$ , $c = 3 \times 10^8 \, \text{m/s}$ , 1 eV = $1.6 \times 10^{-19} \, \text{J}$ )
A. 414 nm
B. 622 nm
C. 248 nm
D. 700 nm
Answer: A
📝 Use $E = \frac{hc}{\lambda}$ → convert eV to J, then solve.

70. Which of the following is NOT true about photoelectric emission?

A. There is a threshold frequency
B. K.E. of electrons increases with intensity
C. No time lag in emission
D. K.E. increases with frequency
Answer: B
📝 K.E. depends on frequency, not intensity.

✅ NEET 2025 Modern Physics MCQ Questions (Set 8)

71. What is the wavelength of a photon with energy 2.48 eV?

(Use $h = 6.63 \times 10^{-34}$ J·s, $c = 3 \times 10^8$ m/s, 1 eV = $1.6 \times 10^{-19}$ J)
A. 250 nm
B. 500 nm
C. 1240 nm
D. 248 nm
Answer: D
📝 $\lambda = \frac{hc}{E} = \frac{1240}{2.48} \, \text{nm} \approx 500 \, \text{nm}$
Correction: Actually, it's ~500 nm. So Answer: B

72. A photon and an electron have the same momentum. Which has more energy?

A. Electron
B. Photon
C. Both have equal energy
D. Cannot be determined
Answer: A
📝 Photon: $E = pc$ , Electron: $E = \frac{p^2}{2m}$ . Since c >> (p/2m), electron has less energy.

Correction: Photon has more energy because of speed $c$ .
✅ Answer: B

73. In Bohr’s hydrogen atom, the ratio of radii of orbits $r_3 : r_1$ is:

A. 3
B. 9
C. 1/3
D. 1/9
Answer: B
📝 Bohr radius $r_n \propto n^2$ → $r_3/r_1 = 9$

74. What is the threshold frequency for a metal with work function 2 eV?

(Planck’s constant $h = 6.63 \times 10^{-34}$ , $1 \, \text{eV} = 1.6 \times 10^{-19} \, \text{J}$ )
A. $4.84 \times 10^{14} \, \text{Hz}$
B. $3.03 \times 10^{14} \, \text{Hz}$
C. $1.21 \times 10^{15} \, \text{Hz}$
D. $2.42 \times 10^{14} \, \text{Hz}$
Answer: A
📝 $f = \frac{\phi}{h} = \frac{2 \times 1.6 \times 10^{-19}}{6.63 \times 10^{-34}} \approx 4.84 \times 10^{14} \, \text{Hz}$

75. A nucleus emits a positron. What happens to its atomic number?

A. Increases by 1
B. Decreases by 1
C. Unchanged
D. Decreases by 2
Answer: B
📝 Positron emission: Proton → Neutron, so atomic number ↓ by 1

76. The de Broglie wavelength of a particle is halved when:

A. Velocity is halved
B. Mass is doubled
C. Momentum is doubled
D. All of the above
Answer: C
📝 $\lambda = \frac{h}{p}$ , so doubling $p$ halves $\lambda$

77. Which spectral line in hydrogen lies in the UV region?

A. Balmer
B. Paschen
C. Lyman
D. Brackett
Answer: C
📝 Lyman series: transitions ending at n=1 → UV region

78. What is the binding energy per nucleon if total binding energy is 28 MeV for a nucleus with mass number 7?

A. 2 MeV
B. 3 MeV
C. 4 MeV
D. 5 MeV
Answer: D
📝 28 MeV ÷ 7 = 4 MeV/nucleon

Correction: Answer: C

79. The probability of a nuclear reaction depends on:

A. Temperature
B. Pressure
C. Nuclear cross-section
D. Energy of emitted gamma rays
Answer: C

80. A photoelectron is emitted with kinetic energy 1.2 eV. If the work function of the metal is 2.8 eV, what is the energy of incident photon?

A. 1.6 eV
B. 2.8 eV
C. 4.0 eV
D. 1.2 eV
Answer: C
📝 $E = K.E. + \phi = 1.2 + 2.8 = 4.0 \, \text{eV}$

✅ NEET 2025 Modern Physics MCQ Questions (Set 9)

81. Assertion (A): A photon has zero rest mass.

Reason (R): Photon always travels at the speed of light in vacuum.
A. Both A and R are true; R is the correct explanation.
B. Both A and R are true; R is not the correct explanation.
C. A is true, R is false.
D. A is false, R is true.
Answer: A

82. Assertion (A): Gamma rays are not deflected by electric or magnetic fields.

Reason (R): Gamma rays have no charge.
A. Both A and R are true; R is the correct explanation.
B. Both A and R are true; R is not the correct explanation.
C. A is true, R is false.
D. A is false, R is true.
Answer: A

83. In which of the following processes is a neutrino emitted?

A. Alpha decay
B. Gamma decay
C. Beta⁻ decay
D. Positron annihilation
Answer: C
📝 In beta⁻ decay: Neutron → Proton + Electron + Antineutrino

84. What is the stopping potential for light of frequency $8 \times 10^{14} \, \text{Hz}$ falling on a metal with work function $2.65 \, \text{eV}$ ?

(Use $h = 6.63 \times 10^{-34} \, \text{J·s}$ , $e = 1.6 \times 10^{-19} \, \text{C}$ )
A. 1.6 V
B. 2.5 V
C. 0.65 V
D. 3.1 V
Answer: C
📝 $E = h\nu \approx 3.3 \, \text{eV}; \, V_0 = \frac{E - \phi}{e} = 3.3 - 2.65 = 0.65 \, \text{V}$

85. Which of the following is not conserved in beta decay?

A. Mass number
B. Atomic number
C. Energy
D. Lepton number
Answer: B
📝 Atomic number changes; mass number remains the same.

86. A metal has a work function of 5 eV. What is the cutoff wavelength for photoelectric emission?

(Use $h = 6.63 \times 10^{-34}$ , $c = 3 \times 10^8$ , $1 \, \text{eV} = 1.6 \times 10^{-19}$ )
A. 250 nm
B. 310 nm
C. 410 nm
D. 500 nm
Answer: B
📝 Use $\lambda = \frac{hc}{\phi} \approx \frac{1240}{5} = 248 \, \text{nm}$
Correction: Answer is A

87. Which line of hydrogen spectrum lies in the IR region?

A. Lyman series
B. Balmer series
C. Paschen series
D. None
Answer: C

88. The time required for a radioactive substance to decay to 1/16th of its original mass is four half-lives. If $T_{1/2} = 5 \, \text{min}$ , find total time:

A. 15 min
B. 20 min
C. 25 min
D. 30 min
Answer: B
📝 4 half-lives = $4 \times 5 = 20 \, \text{min}$

89. In photoelectric effect, emission of electrons occurs only when:

A. Intensity is high
B. Wavelength is low
C. Frequency is below threshold
D. Frequency is above threshold
Answer: D

90. Assertion (A): Binding energy per nucleon is highest for Iron (Fe).

Reason (R): Fe is the heaviest stable nucleus.
A. Both A and R are true; R is the correct explanation.
B. Both A and R are true; R is not the correct explanation.
C. A is true, R is false.
D. A is false, R is true.
Answer: C
📝 Fe has highest binding energy per nucleon, but it’s not the heaviest nucleus.

✅ NEET 2025 Modern Physics MCQ Questions (Set 10)

91. The energy of a photon is inversely proportional to:

A. Frequency
B. Wavelength
C. Velocity
D. Momentum
Answer: B
📝 $E = h\nu = \frac{hc}{\lambda}$ , so energy ∝ 1/λ.

92. A particle has de Broglie wavelength 0.1 nm and velocity $2 \times 10^6 \, \text{m/s}$ . Its mass is:

A. $3.3 \times 10^{-27} \, \text{kg}$
B. $3.3 \times 10^{-30} \, \text{kg}$
C. $6.6 \times 10^{-34} \, \text{kg}$
D. $1.05 \times 10^{-34} \, \text{kg}$
Answer: A
📝 $\lambda = \frac{h}{mv} \Rightarrow m = \frac{h}{\lambda v}$

93. In the photoelectric effect, if the frequency of the incident light is doubled, the kinetic energy of photoelectrons:

A. Doubles
B. Halves
C. Quadruples
D. Remains unchanged
Answer: A
📝 K.E. $= h\nu - \phi$ , so K.E. ∝ frequency.

94. The Bohr radius corresponds to the radius of:

A. 1st orbit of hydrogen atom
B. 2nd orbit of hydrogen atom
C. 1st orbit of helium ion
D. Ground state radius of any atom
Answer: A

95. Half-life of a radioactive isotope is 10 days. The time taken for 75% of it to decay is:

A. 10 days
B. 15 days
C. 20 days
D. 30 days
Answer: B
📝 75% decay = 1/4 remaining = 2 half-lives → 2 × 10 = 20 days
Correction: Actually, 75% decay means 25% remains = (1/2)^n = 1/4 → n=2 → time = 20 days

96. Which of the following is a property of alpha particles?

A. High penetrating power
B. Charge +2e
C. No mass
D. Deflected towards negative plate only
Answer: B

97. The binding energy of a nucleus is the energy required to:

A. Break it into nucleons
B. Change it into another element
C. Convert it to energy
D. Make it radioactive
Answer: A

98. In beta plus decay, which particle is emitted?

A. Electron
B. Positron
C. Neutron
D. Proton
Answer: B

99. The frequency of visible light is approximately:

A. $10^{12} \, \text{Hz}$
B. $10^{15} \, \text{Hz}$
C. $10^{18} \, \text{Hz}$
D. $10^{9} \, \text{Hz}$
Answer: B

100. The mass defect of a nucleus is:

A. Difference between actual and expected mass
B. Mass converted into energy
C. Difference between mass of nucleons and nucleus
D. All of the above
Answer: D

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NEET Physics: Modern Physics MCQ Questions for Quick Revision (2025)

NEET Physics: Modern Physics MCQ Questions for Quick Revision (2025)

📘 NEET Modern Physics Important Topics

✅ Modern Physics MCQ Questions for NEET 2025

1. The energy of a photon is 3.3 × 10⁻¹⁹ J. What is its frequency? (Planck's constant h = 6.6 × 10⁻³⁴ J·s)

2. In the photoelectric effect, increasing the intensity of incident light increases:

3. The de Broglie wavelength of an electron accelerated by a potential difference of 100 V is approximately:

4. According to Bohr’s model, the angular momentum of an electron in the nth orbit is proportional to:

5. A radioactive substance has a half-life of 10 days. After 30 days, the fraction of the substance remaining is:

6. The energy released in the nuclear fission of one uranium-235 atom is approximately:

7. The minimum energy required to remove an electron from the metal surface is known as:

8. X-rays are produced when:

9. The binding energy per nucleon is maximum for:

10. The stopping potential in a photoelectric experiment is directly proportional to:

✅ Continued: Modern Physics MCQ Questions for NEET 2025

11. Which of the following has the shortest de Broglie wavelength, assuming same kinetic energy?

12. Which spectral line in the hydrogen atom corresponds to the transition from n = 4 to n = 2?

13. Which physical quantity remains conserved in both nuclear fission and fusion?

14. The correct expression for the energy of an electron in the nth orbit of hydrogen atom is:

15. A certain radioactive element decays such that 75% of the sample disappears in 2 hours. What is the half-life?

16. In a nuclear reaction, the total mass of products is less than the total mass of reactants. This difference is called:

17. The maximum kinetic energy of photoelectrons emitted depends on:

18. The rest mass energy of an electron is approximately:

19. A sample has activity of 1000 Bq. After 2 half-lives, what will be the remaining activity?

20. Which of the following statements about Bohr’s atomic model is incorrect?

✅ More NEET 2025: Modern Physics MCQ Questions for Practice

21. Which of the following particles will have the highest velocity if all have the same de Broglie wavelength?

22. The unit of radioactive decay constant (λ) is:

23. Which of the following is not a characteristic of nuclear force?

24. Which radiation is most penetrating in matter?

25. The time in which a radioactive substance reduces to 1/16th of its original amount is:

26. What is the change in atomic number and mass number when a nucleus emits a beta⁻ particle?

27. The process of pair production can occur if the photon energy is at least:

28. If the frequency of incident light is below the threshold frequency, what will happen in the photoelectric effect?

29. In Bohr's model of hydrogen atom, the radius of the nth orbit is proportional to:

30. The number of neutrons in an alpha particle is:

✅ Advanced NEET 2025: Modern Physics MCQ Questions (Set 4)

31. Which isotope is used in radiocarbon dating?

32. A nucleus with atomic number Z and mass number A emits an alpha particle. The new nucleus has:

33. The mass defect of a nucleus is directly related to its:

34. Which of the following best explains the stability of the nucleus?

35. The relation between binding energy (BE) and mass defect (Δm) is:

36. The number of electrons in the first Bohr orbit of hydrogen is:

37. If the half-life of a radioactive element is 5 days, how much of a 20g sample will remain after 15 days?

38. The stopping potential in a photoelectric experiment is zero when:

39. The wave nature of electrons is confirmed by:

40. In photoelectric emission, the energy of the ejected electron increases with:

✅ NEET 2025 Modern Physics MCQ Questions (Set 5)

41. The number of photons emitted per second by a monochromatic light source of power 1 W and wavelength 500 nm is approximately:

42. In a hydrogen atom, the wavelength of radiation emitted during the transition from n = 3 to n = 2 is called:

43. Which quantity does not change during a nuclear reaction?

44. A sample initially contains 80 g of a radioactive material. After 2 hours, only 10 g remains. What is its half-life?

45. X-rays are produced when:

46. What happens to the wavelength of emitted radiation as an electron jumps from n = 4 to n = 2 compared to n = 3 to n = 2 in hydrogen atom?

47. What is the effect of increasing the frequency of light beyond the threshold frequency in photoelectric effect?

48. A radioactive isotope has a decay constant of 0.001 s−10.001 \, \text{s}^{-1}0.001s−1. What is its half-life?

49. Which experiment proved the wave nature of electrons?

50. Which one of the following statements is true about gamma radiation?

✅ NEET 2025 Modern Physics MCQ Questions (Set 6)

51. If the energy of an electron in the second orbit of hydrogen atom is -3.4 eV, what is the energy in the fourth orbit?

52. The kinetic energy of a photoelectron depends on:

53. A sample undergoes 3 half-lives. What percentage of the original nuclei remain?

54. The energy released when an electron jumps from n = 5 to n = 1 in a hydrogen atom will be:

55. The photoelectric effect supports which theory of light?

56. When a β⁻ particle is emitted:

57. If the de Broglie wavelength of a particle is 0.02 nm, and its momentum is p, what is its mass if speed v = 3 × 10⁵ m/s?

58. Which of the following is true regarding alpha decay?

59. Gamma radiation differs from X-rays mainly in:

60. If 75% of a radioactive substance decays in 6 hours, its half-life is:

✅ NEET 2025 Modern Physics MCQ Questions (Set 7)

61. Which of the following transitions in the hydrogen atom emits radiation with the highest frequency?

62. In the Davisson-Germer experiment, electron diffraction confirmed:

63. A sample has a half-life of 1 hour. How much of the original sample remains undecayed after 5 hours?

64. The mass number of a nucleus changes when it emits:

65. Which of the following has the maximum penetrating power?

66. What is the order of energy of visible photons?

67. When an electron falls from n = 5 to n = 2, the emitted photon lies in which region?

68. What is the dimension of Planck’s constant (h)?

69. A photon has energy 3 eV. What is its wavelength?

70. Which of the following is NOT true about photoelectric emission?

**43. Which quantity does not change during a nuclear reaction?**

48. A radioactive isotope has a decay constant of $0.001 \, \text{s}^{-1}$ . What is its half-life?

73. In Bohr’s hydrogen atom, the ratio of radii of orbits $r_3 : r_1$ is:

84. What is the stopping potential for light of frequency $8 \times 10^{14} \, \text{Hz}$ falling on a metal with work function $2.65 \, \text{eV}$ ?

88. The time required for a radioactive substance to decay to 1/16th of its original mass is four half-lives. If $T_{1/2} = 5 \, \text{min}$ , find total time:

92. A particle has de Broglie wavelength 0.1 nm and velocity $2 \times 10^6 \, \text{m/s}$ . Its mass is: