Question

In the case of the photo-electric effect, which of the following sentences is NOT TRUE?
a. The photo-electrons are emitted only when the frequency of incident radiation is greater than the threshold frequency.
b. There is no time lag between incidence of light and emission of electrons.
c. The rate of photo-electric emission is independent of the intensity of incident radiation.
d. The maximum kinetic energy of emitted photo-electrons depends on the frequency of incident radiation.

• A. d
• B. c
• C. a
• D. b

Hint:

Recall that the number of photoelectrons emitted per second increases with the intensity of the incident light.

Answer 1

The Correct Option is B

Step 1: Approach
Pick the statement that contradicts the photon picture of light.

Step 2: Elimination
Statements a, b and d all match Einstein's photoelectric equation and observations.

Step 3: Why the other options fail
Option (A) d, option (C) a and option (D) b are correct statements, so they cannot be the answer. Only statement c, option (B), is wrong, since the photocurrent grows with intensity.

Final Answer:
Statement c is the one that is not true. \[ \boxed{\text{(B) }\text{c}} \]