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:

Assertion (A):

• In the photoelectric effect, electrons are emitted from a metal surface when light of frequency greater than the threshold frequency ($\nu_0$) is incident on it.
• To suppress the emission of electrons, a negative potential (called the stopping potential $V_s$) is applied to the metal surface.
• If this potential is large enough, it can completely stop the most energetic photoelectrons from reaching the anode.
  Assertion (A) is correct.

Reason (R):

According to Einstein’s photoelectric equation:

• $$K_{\text{max}} = h\nu - \phi$$

The stopping potential $V_s$ is related to the maximum kinetic energy as:

• $$eV_s = K_{\text{max}} = h\nu - \phi$$

Since $V_s$ is directly proportional to the frequency $\nu$, it varies linearly with frequency (for $\nu > \nu_0$).
 Reason (R) is also correct.