Chapter 11 Dual Nature of Radiation and Matter is one of the most concept-based and scoring chapters in Class 12 Physics. With the Class 12 Physics Board Exam 2026 scheduled for February 21, 2026, students must now focus on Dual Nature of Radiation and Matter Class 12 Important Questions to strengthen conceptual clarity and numerical accuracy.
This chapter introduces groundbreaking concepts such as the photoelectric effect, Einstein’s photoelectric equation, and de Broglie wavelength.
Since the questions are often formula-based and reasoning-oriented, practicing Dual Nature of Radiation and Matter Class 12 Physics Question Answers thoroughly can help students secure easy marks.
Along with numericals, students must also revise Dual Nature of Radiation and Matter Class 12 MCQ patterns, as competency-based and assertion-reason questions are frequently asked from this unit.
Dual Nature of Radiation and Matter Class 12 Important Questions
Preparing Dual Nature of Radiation and Matter Class 12 Important Questions helps students understand the wave-particle duality concept clearly. The chapter mainly focuses on photoelectric effect, experimental observations, Einstein’s photoelectric equation, and other concepts.
Below are the Dual Nature of Radiation and Matter Class 12 MCQs as well the questions and answers:
1. The energy of emitted photo electron depends upon [Delhi 2001, SQP 2014]
(A) Intensity of light
(B) Wavelength of light
(C) Work-function of metal
(D) None of these
2. Mass of a photon of frequency ν is given by
3. If the intensity of light falling on a metal is increased, then [Delhi 2016]
(A) K.E. of photoelectrons increases
(B) photoelectric current increases
(C) K.E. of photoelectrons decreases
(D) photoelectric current remains constant
(B)
Sol. For a given photosensitive material and frequency of incident radiation above the threshold frequency, emission of photoelectrons (i.e., photoelectric current) is directly proportional to the intensity of the incident light. Therefore if the intensity of light falling on a metal is increased, then photoelectric current will also increase. Thus (B) is correct option.
4. Show graphically the variation of the de-Brogile wavelength (λ) with the potential (V) through which an electron is accelerated from rest. [OD 2020, Comp 2019]
5. In photoelectric effect, why should the photoelectric current increase as the intensity of monochromatic radiation incident on a photosensitive surface is increased? Explain. [Foreign 2014]
Sol. The photoelectric current increases proportionally with the increase in intensity of incident radiation. Larger the intensity radiation, larger is the number of incident photons and hence larger is the number of electrons ejected from the photosensitive surface.
6. Use de-Broglie's hypothesis to write the relation for nth radius of Bohr orbit in terms of Bohr's quantization condition of orbital angular momentum. [OD 2010]
7. 1. Show that the de Broglie wavelength of electron of energy E is given by the relation,
2. Why is the belt of a Van de Graaff generator made of insulating material? [Delhi 2013]
Sol. 1. Let an electron of charge e having mass m be accelerated from rest through a potential difference v, than.
2. Because this charges taken by belt do not spread out but it resides on same place. Charges are send by the belt to the pointed conductor. If the belt is conductor material then charges spread out on the whole belt and the system does not run systematically.
8. Write the relationship of de-Broglie wavelength λ associated with a particle of mass m in terms of its kinetic energy E. [Comp 2010, SQP 2013]
9. Plot a graph showing the variation of photoelectric current with intensity of light. The work function for the following metals is given Na: 2.75eV and Mo: 4.175 eV. Which of these will not give photoelectron emission from a radiation of wavelength 33000Å from a laser beam? What happened if the source of laser beam is brought closer? [Foreign 2013]
10. A proton and an electron have same velocity. Which one has greater de-Broglie wavelength and why?
Important Topics to Revise Before the Board Exam
Here are some important topics students must revise before the board exam:
1. Photoelectric Effect
Understand experimental observations and graphical representation of stopping potential vs frequency.
2. Einstein’s Photoelectric Equation
Derivation and numerical application are frequently tested.
3. Threshold Frequency and Work Function
Direct formula-based questions are common.
4. de Broglie Wavelength
Important for both derivations and numericals.
5. Wave-Particle Duality Concept
Often asked in reasoning or short answer format.
How to Revise Dual Nature of Radiation and Matter Class 12 Question Answers
With the board exam approaching on February 21, 2026, follow this revision strategy:
1. Revise All Formulas Daily
Keep a formula sheet including Einstein’s equation and de Broglie relation.
2. Practice 8–10 Numericals
Solve different types of numericals from Dual Nature of Radiation and Matter Solutions.
3. Understand Graph-Based Questions
Interpret stopping potential vs frequency graphs carefully.
4. Attempt Mixed Question Sets
Combine short answers, long answers, and Dual Nature of Radiation and Matter Class 12 MCQ.
5. Solve Previous Year Questions
Board questions from this chapter are often repeated with minor modifications.
Focused preparation of Dual Nature of Radiation and Matter Class 12 Important Questions can easily help students secure 4–6 marks from this chapter alone.