As the intensity of incident light increases,

What is the intensity of radiation (light)?

Threshold frequency for a metal is $15 \times 10^{14} \,Hz$. The light of wavelength $6000 \text{ Å}$ falls on the metal surface. Which one of the following statements is correct? [velocity of light, $c = 3 \times 10^{8} \,m/s$]

Consider the two following statements $A$ and $B$, and identify the correct choice given in the answers :
$(A)$ In photovoltaic cells, the photoelectric current produced is not proportional to the intensity of incident light.
$(B)$ In gas-filled photoemissive cells, the velocity of photoelectrons depends on the wavelength of the incident radiation.

For a given source,with an increase in intensity of incident radiation,the . . . . . .

Light of wavelength $4000 \ \mathring A$ is incident on a sodium surface,where the threshold wavelength for photoemission is $5420 \ \mathring A$. The work function of sodium is ............ $eV$.