Practice tests · NEET

NEET Modern Physics: 5 practice MCQs with answers

By the PrepMatic team · Updated 9 Oct 2026 · 4 min read

Modern Physics is the NEET name for three NMC units taken together: Dual Nature of Matter and Radiation, Atoms and Nuclei, and Electronic Devices. The questions are short and formula-based, so this is among the more reliable scoring areas. The five MCQs below cover the photoelectric effect, de Broglie wavelength, Bohr energy levels, half-life and the p-n junction, at NCERT Class 12 level.

What this chapter covers in the NEET syllabus

The topics, following the NCERT Class 12 chapters Dual Nature of Radiation and Matter, Atoms, Nuclei and Semiconductor Electronics, are:

• Dual nature: photoelectric effect, Einstein's equation, work function, threshold frequency, stopping potential and the de Broglie hypothesis.
• Atoms: the Rutherford model, the Bohr model of hydrogen, energy levels and the line spectra.
• Nuclei: nuclear size, mass defect and binding energy, radioactivity, half-life, fission and fusion.
• Electronic devices: semiconductors, the p-n junction diode in forward and reverse bias, its use as a rectifier, and logic gates.

Check the NMC syllabus PDF for the sub-topics currently listed under each unit.

Five practice MCQs on Modern Physics

Question 1

Light of photon energy 5 eV falls on a metal surface with a work function of 2 eV. The maximum kinetic energy of the emitted photoelectrons is:

• A. 7 eV
• B. 3 eV
• C. 2.5 eV
• D. 10 eV

Question 2

An electron and a proton have the same kinetic energy. Which has the longer de Broglie wavelength?

• A. The proton
• B. Both have the same wavelength
• C. The electron
• D. Neither, since particles have no wavelength

Question 3

The energy of an electron in the n = 2 level of a hydrogen atom is (ground-state energy −13.6 eV):

• A. −13.6 eV
• B. −6.8 eV
• C. −1.51 eV
• D. −3.4 eV

Question 4

A radioactive sample of 80 g has a half-life of 10 days. The mass of the sample left after 30 days is:

• A. 10 g
• B. 20 g
• C. 40 g
• D. 26.7 g

Question 5

When a p-n junction diode is forward biased, the width of its depletion region:

• A. increases
• B. decreases
• C. remains unchanged
• D. becomes infinite

Answers and explanations

1. B. Einstein's photoelectric equation gives KEmax = hν − φ = 5 − 2 = 3 eV. The work function is the minimum energy needed to free an electron, so it is subtracted, not added.
2. C. The de Broglie wavelength is λ = h/p = h/√(2mK). For the same K, the lighter particle has the smaller momentum and so the longer wavelength. The electron is about 1836 times lighter than the proton.
3. D. En = −13.6/n² eV, so for n = 2, E = −13.6/4 = −3.4 eV. Option C, −1.51 eV, is the n = 3 level, and option A is the ground state.
4. A. 30 days is three half-lives, so the mass is 80 × (1/2)³ = 80/8 = 10 g. Each half-life halves what is left at that moment, not the original amount.
5. B. Forward bias pushes majority carriers toward the junction, which narrows the depletion region and lowers the barrier. In reverse bias the region widens and almost no current flows.

How to prepare Modern Physics

• Learn the photoelectric facts in a list. KEmax depends on frequency, not intensity. The photocurrent depends on intensity. Below the threshold frequency there is no emission, however bright the light. Stopping potential gives KEmax = eV0.
• Memorise the Bohr results for hydrogen: En = −13.6/n² eV, radius rn proportional to n², and the spectral series (Lyman, Balmer, Paschen) with their final levels 1, 2 and 3. For hydrogen-like ions multiply the energy by Z².
• Handle radioactivity with N = N0 (1/2)^(t/T). Count the number of half-lives first. Know the relation between half-life and decay constant, T = 0.693/λ, and mean life.
• Keep nuclear numbers ready. The energy equivalent of 1 u is 931.5 MeV, and the nuclear radius is proportional to A^(1/3). Binding energy per nucleon curves explain fission and fusion.
• Do not skip electronics. Diode characteristics, the rectifier and basic logic gates are quick marks once you know the truth tables.

Revise this unit in short, frequent bursts: formula sheet in the morning, five questions at night. For the wider Physics plan, see the NEET Physics preparation guide, and for the full unit list, the NEET syllabus.

Take a full Modern Physics test on PrepMatic

This unit is short and formula-based, which makes it a good candidate for a quick topic test: about 15 questions in 30 minutes on PrepMatic, scored with NEET's negative marking. If you are unsure whether Physics is your weakest subject, take the free assessment first. More chapters are on the practice hub.

← All practice tests