Modern Physics is the most scoring unit in NEET Physics. Its three chapters, Dual Nature of Radiation and Matter, Atoms, and Nuclei, are short, formula-based and almost free of long calculations. This modern physics NEET PYQ analysis shows which question types NTA repeats and the shortcuts that solve them in seconds.
For concept building, pair this with our modern physics preparation guide, and see the bigger picture in our complete NEET Physics strategy. This article focuses on what past papers actually ask.
Want to test yourself first? Solve the free Dual Nature of Radiation and Matter PYQs, Atoms PYQs and Nuclei PYQs, then use this guide to fix the gaps.
Table of Contents
Why Modern Physics Is the Best Return on Time
NEET usually asks four to five questions from these three chapters together. The theory fits in about 40 NCERT pages, so no other Physics unit gives as many marks for so little reading.
Keep the class notes open while you revise: Dual Nature class 12 notes, Atoms class 12 notes and Nuclei class 12 notes.
Modern Physics NEET PYQ Analysis: The Repeated Question Types
After sorting a decade of NEET physics PYQs from these three chapters, the questions fall into six families.
| Question family | Frequency | What it tests |
|---|---|---|
| Photoelectric effect | Most frequent | Einstein’s equation, stopping potential, graphs |
| de Broglie wavelength | Very frequent | Dependence on momentum, energy and voltage |
| Bohr model of hydrogen | Very frequent | Radius, energy and speed in the nth orbit |
| Spectral series | Regular | Series, region, number of lines |
| Binding energy | Very frequent | Mass defect, energy released, stability |
| Nuclear size and density | Regular | R = R₀A^(1/3), constant density |
For a quick warm-up before the full set, try these modern physics warm-up questions.
Photoelectric Effect
- Einstein’s equation: K_max = hν − φ, where φ is the work function.
- Stopping potential: eV₀ = K_max.
- Threshold frequency: ν₀ = φ/h. Below it, no electrons are emitted, whatever the intensity.
- Shortcut: E (in eV) = 1240/λ (in nm).
What depends on what:
| Change | Effect |
|---|---|
| Intensity increased (same frequency) | Photocurrent increases; K_max and stopping potential unchanged |
| Frequency increased (same intensity) | K_max and stopping potential increase |
In the graph of stopping potential against frequency, the slope is h/e for every metal. Only the intercept changes with the metal. Photoelectric effect questions are usually built on this table or this graph.
de Broglie Wavelength
- λ = h/p = h/mv
- In terms of kinetic energy: λ = h/√(2mK)
- For a charge q accelerated through V: λ = h/√(2mqV)
- For an electron: λ = 12.27/√V Å
So the de Broglie wavelength falls as momentum rises. For the same kinetic energy, the heavier particle has the shorter wavelength. For the same momentum, all particles have the same wavelength.
Bohr Model of Hydrogen
For a hydrogen-like atom of atomic number Z, in the nth orbit:
| Quantity | Formula | Depends on |
|---|---|---|
| Radius | 0.529 n²/Z Å | n²/Z |
| Energy | −13.6 Z²/n² eV | Z²/n² |
| Speed | 2.18 × 10⁶ Z/n m/s | Z/n |
| Angular momentum | nh/2π | n |
- Kinetic energy = −(total energy); potential energy = 2 × (total energy).
- Ionisation energy of hydrogen from the ground state is 13.6 eV.
Spectral series: Lyman (to n = 1, ultraviolet), Balmer (to n = 2, visible), Paschen (to n = 3, infrared). The number of spectral lines from the nth level is n(n − 1)/2.
The Bohr model applies only to single-electron species such as H, He⁺ and Li²⁺.
Nuclei: Size, Mass Defect and Binding Energy
- Radius: R = R₀A^(1/3), with R₀ ≈ 1.2 fm.
- Nuclear density is about 2.3 × 10¹⁷ kg/m³ and is the same for all nuclei.
- Mass defect: Δm = [Zm_p + (A − Z)m_n] − M.
- Binding energy = Δm × c², and 1 u = 931.5 MeV.
- Binding energy per nucleon is highest (about 8.75 MeV) near iron-56, so medium nuclei are the most stable.
- Heavy nuclei release energy by fission; light nuclei release energy by fusion.
- Energy released in a reaction: Q = (binding energy of products) − (binding energy of reactants).
The current syllabus for Nuclei centres on nuclear size, mass-energy, binding energy, fission and fusion. Check the official syllabus before spending time on the radioactive decay law.
Worked PYQ-Pattern Questions
Q1. Light of photon energy 4 eV falls on a metal of work function 2.5 eV. What is the stopping potential?
Answer: 1.5 V. K_max = 4 − 2.5 = 1.5 eV, so V₀ = 1.5 V.
Q2. The intensity of light is doubled at the same frequency. What happens to K_max and the photocurrent?
Answer: K_max is unchanged; the photocurrent doubles.
Q3. An electron in hydrogen jumps from n = 3 to n = 1. What is the energy of the photon emitted?
Answer: 12.09 eV. E = 13.6 (1 − 1/9) = 12.09 eV.
Q4. What is the ratio of the radii of nuclei with mass numbers 27 and 64?
Answer: 3 : 4. R ∝ A^(1/3), and the cube roots are 3 and 4.
Q5. The kinetic energy of a particle becomes four times. How does its de Broglie wavelength change?
Answer: It is halved. λ ∝ 1/√K.
Common Traps to Avoid
- Saying K_max increases with intensity
- Using the electron formula 12.27/√V for a proton
- Mixing up the n-dependence of radius, energy and speed
- Forgetting that total energy in a Bohr orbit is negative
- Assuming a heavier nucleus is denser
Practise Every Modern Physics PYQ
The fastest way to lock in these patterns is to solve real past questions, chapter by chapter. All three chapters are available chapter-wise, free:
👉 Solve Dual Nature of Radiation and Matter NEET PYQs
One chapter a day is enough. In three days, the whole unit is done.
Conclusion
This unit is short, predictable and generous. Use this modern physics NEET PYQ analysis to master the photoelectric equation, the wavelength relations, the Bohr formulas and binding energy. Then practise until each question takes under a minute.
❓ FAQ
Q: How many questions come from Modern Physics in NEET? A: Usually four to five questions from Dual Nature, Atoms and Nuclei together, which is up to 20 marks.
Q: Which chapter of Modern Physics is most important? A: Dual Nature of Radiation and Matter gives the most questions, mainly on the photoelectric effect and matter waves. Atoms and Nuclei follow closely.
Q: Is Modern Physics easy for NEET? A: Yes. The chapters are short and the questions are mostly direct formula applications, so it is one of the most scoring units.
Q: Does stopping potential depend on intensity? A: No. Stopping potential depends on the frequency of light and the work function of the metal, not on intensity.
Q: How should I revise this unit? A: Use a modern physics NEET PYQ analysis to list the repeated question types, make a one-page formula sheet, and solve past questions chapter-wise.
Q: Where can I practise Modern Physics NEET PYQs for free? A: You can solve every previous year question from all three chapters for free using the practice links in this article.