During collision of electrons and photons,

Assertion: Alkali metals are most suitable for photoelectric effect.

Reason: The work function of alkali metals is small, so even the radiations of small energy are able to cause the photoelectric effect.

Assertion: If the intensity of incident radiation on a metal is doubled, then $\mathrm{K}.\mathrm{E}.$ of photoelectrons emitted will be doubled.

Reason: $\mathrm{K}.\mathrm{E}.=\frac{1}{2}m{v}^2=h\left(\nu -{\nu }_0\right)$where $v$ is the velocity of photo electrons.

The symbol for photocell is