Question

Assertion: In photoelectric effect, on increasing the intensity of light, both the number of electrons emitted and kinetic energy of each of them get increased but photoelectric current remains unchanged.
Reason: The photoelectric current depends only on wavelength of light.
A. Both assertion and reason are correct and reason is the correct explanation for assertion.
B. Both assertion and reason are correct but reason is not the correct explanation for assertion.
C. Assertion is correct but Reason is incorrect.
D. Both assertion and reason are incorrect.

Answer 1

Hint: Here, we have to consider the photoelectric effect and try to understand the question because the whole concept is dependent on photoemission. The energy of a photon depends on the frequency of the light wave that is incident on the metal surface. On the basis of this we have to solve this question.

Complete step by step solution:
Let us see the assertion first, the assertion says that in photoelectric effect on increasing intensity of light the kinetic energy increases but it is not true since kinetic energy of the photon depends on the frequency of the light not on its intensity so the assertion is incorrect.

Now, let us talk about reason, reason says that photoelectric current depends only on wavelength of light which is incorrect because it also depends on intensity of light intensity increases the current increases. But, the reason for the assertion is incorrect. Therefore, both assertion and reason are incorrect.

Hence, the correct answer is option D.

Additional information: Heinrich Rudolf Hertz of Germany developed the photoelectric phenomenon in 1887. In conjunction with his work on radio waves, Hertz discovered that when ultraviolet light shines on two metal electrodes with a voltage connected across them, the light affects the voltage at which sparking occurs. Philipp Lenard, another German physicist, elucidated the relationship between light and electricity (thus photoelectric) in 1902.

Note: Photoelectric current not only depends on wavelength of light but it also depends on intensity of light. Also, the kinetic energy only depends on the frequency of photons emitted. This concept is clearly mentioned in the photoelectric effect.