# Physics Questions and Answers – Experimental Study of Photoelectric Effect

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This set of Physics Aptitude Test for Class 12 focuses on “Experimental Study of Photoelectric Effect”.

1. Which of the following increases the maximum kinetic energy of the photoelectrons emitted?
a) Increasing the frequency of the incident beam
b) Increasing the velocity of the electrons
c) Decreasing the frequency of the incident beam
d) Increasing the mass of the photoelectrons

Explanation: The maximum kinetic energy of the photoelectrons can be increased by increasing the frequency of the incident beam and at the same time keeping the number of incident photons fixed. Now, this would result in a proportionate increase in energy, and in this way, the maximum kinetic energy can be increased.

2. Who is responsible for the photoelectric effect experiment?
a) Albert Einstein
b) Max Planck
c) Heinrich Hertz
d) de – Broglie

Explanation: German physicist Heinrich Rudolf Hertz discovered the photoelectric effect in 1887 when he was working in connection with his work on radio waves. During this time, Hertz observed that, when ultraviolet light shines on two metal electrodes with a voltage applied across them, the light changes the voltage at which sparking takes place. This led to his discovery of the photoelectric effect experiment.

3. Identify the conclusion of the photoelectric experiment from the following.
a) Photons are smaller than the electrons
b) The energy in light comes as small packets
c) The energy in light comes as huge packets of energy
d) The energy released by the photoelectric effect is very less

Explanation: The conclusion drawn from the experiment of the photoelectric effect is that the energy in light comes as small packets. These small packets of energy are known as quantum of energy or a photon. The magnitude of these is proportional to the frequency of the wave.
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4. The photoelectric effect is commonly found in solar panels.
a) True
b) False

Explanation: Yes, this is a true statement. Solar panels work on the basic principle that when light strikes the cathode, it causes the emission of electrons, which in turn will produce an electric current. Therefore, the photoelectric effect finds application in solar panels.

5. Find the odd one out.
a) Chlorine
b) Sodium
c) Oxygen
d) Helium

Explanation: In this, sodium is the odd one out because, sodium, being an alkali metal, is photosensitive while the others are not photosensitive materials. Sodium metal emits electrons even when ordinary light falls on it. Therefore, it is known as a photosensitive material.

6. Pick out the apparatus used in the experiment of the photoelectric effect from the following.
a) Electron gun
b) Vacuum tubes
c) Metal tubes
d) Glass tubes

Explanation: The apparatus used in the experiment of the photoelectric effect involves an evacuated glass tube. Two metal electrodes, a collector, and a metal plate are enclosed in this glass tube. This glass tube is provided with a side quartz window. The metal plate acts as the photoelectron emitter.

Sanfoundry Global Education & Learning Series – Physics – Class 12.