1. In the photoelectric effect, the maximum kinetic energy of emitted electrons is given by Einstein’s photoelectric equation:

$K_{\max} = h\nu - \phi$

where:

• $h$ = Planck’s constant
• $\nu$ = frequency of incident radiation
• $\phi$ = work function of the metal

2. The stopping potential $V_0$ is the potential needed to stop the most energetic photoelectrons, so:

$eV_0 = K_{\max}$

Substituting from Einstein’s equation:

$eV_0 = h\nu - \phi$

or,

$V_0 = \frac{h\nu - \phi}{e}$

3. From this expression, the stopping potential depends directly on the frequency $\nu$ of the incident radiation.

4. Now evaluate the options:

• A: Phase — No, stopping potential does not depend on phase.
• B: Frequency — Yes, correct.
• C: Amplitude — No, amplitude affects field strength, not stopping potential directly.
• D: Intensity — No, intensity affects the number of emitted electrons (photoelectric current), not the stopping potential.

Therefore, the correct answer is:

$\boxed{\text{B: Frequency}}$