Chapter Exam

Chapter 12: Dual Nature of Radiation and Matter — Online MCQ Test

Q: The minimum energy required to remove an electron from a metal surface is called:

Answer: B. Work function — The work function is the minimum energy needed to liberate an electron from the metal surface. It is usually denoted by ϕ.

Q: A beam of light of frequency just above threshold falls on a metal plate. If the intensity is doubled, which result is correct?

Answer: C. Photoelectric current increases — Doubling intensity increases the number of photons incident per second, hence more electrons are emitted and the current increases. The maximum kinetic energy remains unchanged for the same frequency.

Q: A proton and an electron have the same kinetic energy. Which one has the larger de Broglie wavelength?

Answer: B. Electron — For the same kinetic energy, momentum is smaller for the lighter particle. Since λ = h/p, the electron has the larger de Broglie wavelength.

PHYSICS · CLASS 12 INTERMEDIATE 2 YEAR · Telangana State Board

Practice Chapter 12: Dual Nature of Radiation and Matter with a free chapter-wise online MCQ test for Telangana State Board CLASS 12 INTERMEDIATE 2 YEAR PHYSICS. This chapter covers: This chapter details photoelectric effect Hertz Lenard observations Einstein photoelectric equation photon nature and de Broglie matter wave hypothesis.. AI-generated questions from basic to board-exam level, with instant results and explanations.

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Chapter 12: Dual Nature of Radiation and Matter — Important Questions & Answers (FAQ)

Frequently asked questions from Telangana State Board CLASS 12 INTERMEDIATE 2 YEAR PHYSICS — Chapter 12: Dual Nature of Radiation and Matter, with answers and explanations. These are sample questions; the exam has its own separate question set.

Which phenomenon could not be explained by the wave theory of light and led to the discovery of the photoelectric effect?

A. Interference
B. Diffraction
C. Emission of electrons from a metal surface by light ✓
D. Polarization

Answer: C. Emission of electrons from a metal surface by light
The photoelectric effect is the emission of electrons from a metal surface when light of suitable frequency falls on it. Classical wave theory failed to explain its observed features.

The minimum energy required to remove an electron from a metal surface is called:

A. Ionization energy
B. Work function ✓
C. Threshold energy
D. Stopping potential

Answer: B. Work function
The work function is the minimum energy needed to liberate an electron from the metal surface. It is usually denoted by ϕ.

Which of the following observations of the photoelectric effect supports the particle nature of light?

A. Intensity of light increases the maximum kinetic energy
B. Photoelectric emission occurs only if frequency is above a certain value ✓
C. Photoelectric current is independent of intensity
D. All wavelengths produce emission if intensity is high enough

Answer: B. Photoelectric emission occurs only if frequency is above a certain value
The existence of threshold frequency shows that energy comes in discrete packets. If the light frequency is below the threshold, no electrons are emitted regardless of intensity.

A beam of light of frequency just above threshold falls on a metal plate. If the intensity is doubled, which result is correct?

A. Maximum kinetic energy doubles
B. Stopping potential doubles
C. Photoelectric current increases ✓
D. Threshold frequency changes

Answer: C. Photoelectric current increases
Doubling intensity increases the number of photons incident per second, hence more electrons are emitted and the current increases. The maximum kinetic energy remains unchanged for the same frequency.

A proton and an electron have the same kinetic energy. Which one has the larger de Broglie wavelength?

A. Proton
B. Electron ✓
C. Both have the same wavelength
D. Cannot be determined

Answer: B. Electron
For the same kinetic energy, momentum is smaller for the lighter particle. Since λ = h/p, the electron has the larger de Broglie wavelength.

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