The threshold wavelength for sodium is $6 \times 10^{-7} \, m$. Photoemission occurs for light of wavelength $\lambda$ if:

When a metallic surface is illuminated with monochromatic light of wavelength $\lambda$,the stopping potential is $5V_0$. When the same surface is illuminated with light of wavelength $3\lambda$,the stopping potential is $V_0$. Then the work function of the metallic surface is:

In a photoelectric experiment,ultraviolet light of wavelength $280 \, nm$ is used with a lithium cathode having a work function $\phi = 2.5 \, eV$. If the wavelength of incident light is switched to $400 \, nm$,find out the change in the stopping potential (in $V$).
$(h = 6.63 \times 10^{-34} \, J \cdot s, c = 3 \times 10^8 \, m/s)$

When green light is incident on the surface of a metal, it emits photo-electrons, but there is no such emission with yellow light. Which one of the following colors can produce the emission of photo-electrons?

Ultraviolet light of wavelength $300 \ nm$ and intensity $1.0 \ W/m^2$ is incident on the surface of a photosensitive material. If $1\%$ of the incident photons produce photoelectrons,the number of photoelectrons emitted from an area of $1.0 \ cm^2$ of the surface is:

When green light is incident on the surface of a metal, it emits photo-electrons, but there is no such emission with yellow light. Which one of the following colours can produce emission of photo-electrons?