# Physics Questions and Answers – Photoelectric Theory and Wave Theory of Light

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This set of Physics Multiple Choice Questions & Answers (MCQs) focuses on “Photoelectric Theory and Wave Theory of Light”.

1. Which theory of light explains the photoelectric effect?
a) Electromagnetic theory
b) Magnetic theory
c) Electric theory
d) Wave theory

Explanation: According to the electromagnetic theory, the photoelectric effect can be attributed to the transfer of energy from the light to an electron. From this point of view, an alteration in the intensity of light will induce changes in the kinetic energy of the electrons emitted from the metal.

2. Which theory of light is wave theory or particle theory?
a) Dynamic physics
b) Static physics
c) Quantum mechanics
d) de – Broglie hypothesis

Explanation: The essential theory of light was further evolved from electromagnetics into quantum mechanics. Einstein believed light is a particle, i.e. a photon and that the flow of these particles (photons) is a wave.

3. Which principle suggests that the intensity of light determines its amplitude?
a) Huygens principle
b) Classic wave theory
c) de – Broglie hypothesis
d) Einstein’s particle theory

Explanation: The principle is the classic wave theory. The classic wave theory states that the intensity of light determines the amplitude of the wave. Therefore, a greater intensity of light will cause the electrons on the metal to oscillate more violently and also to be ejected with greater kinetic energy.
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4. Wave theory explains the photoelectric effect.
a) True
b) False

Explanation: No, this is a false statement. The photoelectric effect cannot be explained by wave theory because, in the photoelectric effect, the electron emissions are immediate without a time delay, whereas in wave theory, the electrons are emitted only after a small instant of time.

5. Why does light travel as a wave?
a) Due to the small packets called photons
b) Due to an electric field
c) Light does not travel as a wave
d) Due to its electromagnetic nature

Explanation: Light travels as a wave due to its electromagnetic nature. This is further facilitated by Maxwell’s equations which states that changing magnetic fields give rise to electric fields and changing electric fields give rise to magnetic fields.
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