Question 52: Dual Nature of Matter and Radiation

Question

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) :
Emission of electrons in photoelectric effect can be suppressed by applying a sufficiently negative electron potential to the photoemissive substance.
Reason (R) :
A negative electric potential, which stops the emission of electrons from the surface of a photoemissive substance, varies linearly with frequency of incident radiation.
In the light of the above statements, choose the most appropriate answer from the options given below :

Accepted Answer

Assertion (A)
is
true
because a sufficiently negative potential can repel and stop the emitted electrons from leaving the surface.
Reason (R)
is
also true
because the stopping potential $V_{	ext{stop}}$ varies linearly with the frequency $
u$ of the incident light ($V_{	ext{stop}} = \frac{h}{e}\,
u - \frac{\phi}{e}$).
However, (R) does
not
directly explain
why
a negative potential suppresses electron emission; it only shows
how much
potential is needed for different frequencies.
Therefore,
both (A) and (R) are true, but (R) is not the correct explanation of (A)
.

Answer

Both (A) and (R) are true and (R) is the correct explanation of (A).

Answer

Both (A) and (R) are true but (R) is not the correct explanation of (A).

Answer

(A) is false but (R) is true

Answer

(A) is true but (R) is false

Dual Nature of Matter and Radiation

Choose the correct answer: