Question

In a photoelectric experiment, increasing the intensity of incident light :

• A. increases the number of photons incident and also increases the K.E. of the ejected electrons.
• B. increases the number of photons incident and the K.E. of the ejected electrons remains unchanged.
• C. increases the frequency of photons incident and increases the K.E. of the ejected electrons.
• D. increases the frequency of photons incident and the K.E. of the ejected electrons remains unchanged.

Hint:

Remember the two key relationships in the photoelectric effect:
- \textbf{Intensity} \(\leftrightarrow\) \textbf{Number of Photons} \(\leftrightarrow\) \textbf{Photoelectric Current}.
- \textbf{Frequency} \(\leftrightarrow\) \textbf{Energy of Photons} \(\leftrightarrow\) \textbf{Kinetic Energy of Electrons} (and Stopping Potential).
Intensity does not affect K.E., and frequency does not affect the number of photons (for a fixed intensity).

Answer 1

The Correct Option is B

The given question is about the photoelectric effect. In this experiment, we analyze how changes in the properties of incident light affect the ejected electrons from a material surface.

Let's analyze the options based on the principles of the photoelectric effect:

1. Intensity of Light: In the context of the photoelectric effect, the intensity of light is related to the number of photons striking the surface.
2. Kinetic Energy (K.E.) of Ejected Electrons: According to Einstein's photoelectric equation, K.E. = h\nu - \phi, where h is Planck’s constant, \nu is the frequency of the incident photon, and \phi is the work function of the material.

Analysis of Options:

1. Increases the number of photons incident and also increases the K.E. of the ejected electrons. - This option is incorrect because increasing intensity increases the number of photons but does not change their energy or frequency, thus the kinetic energy of the electrons remains the same.
2. Increases the number of photons incident and the K.E. of the ejected electrons remains unchanged. - This is the correct answer. Increasing intensity increases the number of photons, leading to more ejected electrons, but since the frequency (which determines K.E.) remains unchanged, the K.E. of the electrons remains the same.
3. Increases the frequency of photons incident and increases the K.E. of the ejected electrons. - This is incorrect as the intensity does not affect the frequency of the photons.
4. Increases the frequency of photons incident and the K.E. of the ejected electrons remains unchanged. - This option is incorrect for the same reason; intensity does not change frequency, and frequency impacts K.E.

Therefore, the correct answer is: Increases the number of photons incident and the K.E. of the ejected electrons remains unchanged.