The work function of a metal surface is $6.2 \ eV$. If the stopping potential for radiation incident on this surface is $5 \ V$,then the incident radiation will be in the ...... region.

$A$ beam of photons with an energy of $10.5 \ eV$ strikes a metal plate. The photoelectrons are emitted with a maximum velocity of $1.6 \times 10^6 \ m \ s^{-1}$. The work function of the metal is (Assume mass of electron $= 9 \times 10^{-31} \ kg$ and charge of electron $= 1.6 \times 10^{-19} \ C$). (in $eV$)

$A$ cobalt $(Co)$ plate is placed at a distance of $1 \,m$ from a point source of power $1 \,W$. Assume a circular area of the plate of radius $r = 1 \,Å$ is exposed to the radiation and ejects photoelectrons. The light energy is considered to be spread uniformly and the work function of cobalt is $5 \,eV$. The minimum time the target should be exposed to the light source to eject a photoelectron (assuming no reflection losses) is: (in $\,s$)

When a photosensitive surface is irradiated by light of wavelengths $\lambda_{1}$ and $\lambda_{2}$,the kinetic energies of the emitted photoelectrons are $E_{1}$ and $E_{2}$ respectively. The work function of the photosensitive surface is

$A$ point source of light emits photons of energy $4.8 eV$ at the rate $10^5$ photons per second. These photons are incident on a photo-sensitive sphere of work function $2.8 eV$ and radius $9 mm$. The sphere is initially neutral and the emitted photoelectrons are instantly swept away. The time after which the photoelectric emission stops is (in $s$)

The work functions for metals $A$, $B$, and $C$ are $1.92 eV$, $2.0 eV$, and $5 eV$ respectively. The metal(s) which will emit photoelectrons for incident radiation of wavelength $4100 Å$ is/are $[h=6.63 \times 10^{-34} J s, e=1.6 \times 10^{-19} C, c=3 \times 10^8 m/s]$.