Photoelectric effect occurs when ultraviolet rays are incident on a metal plate. It does not occur when which of the following are incident?

Light with a frequency of $1.5$ times the threshold frequency is incident on a photosensitive material. If the frequency is halved and the intensity is doubled,what will be the photoelectric current?

When a monochromatic point source of light is at a distance of $0.2\, m$ from a photoelectric cell,the cut-off voltage and the saturation current are respectively $0.6\, V$ and $18.0\, mA$. If the same source is placed $0.6\, m$ away from the photoelectric cell,then

Photo cells convert

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.

The number of photoelectrons emitted varies with which physical quantity?