The threshold wavelength for photoelectric effect from a metal is $200 \ nm$. The maximum kinetic energy of the emitted photoelectrons when radiation of wavelength $100 \ nm$ is incident on the metal is .......... $eV$.

An electron moving with velocity $1.6 \times 10^7 \ m/s$ has a wavelength of $0.4 \ \mathring{A}$. The required accelerating voltage for the electron motion is (charge on electron $= 1.6 \times 10^{-19} \ C$,mass of electron $= 9 \times 10^{-31} \ kg$).

Two radiations of photon energies $1 \; eV$ and $2.5 \; eV$ successively illuminate a photosensitive metallic surface of work function $0.5 \; eV$. The ratio of the maximum speeds of the emitted electrons is

Light of wavelength $\lambda$ strikes a photo-sensitive surface and electrons are ejected with kinetic energy $E$. If the kinetic energy is to be increased to $2E$,the wavelength must be changed to $\lambda'$ where

The maximum kinetic energy of the photo-electrons depends only on

When a metallic surface is illuminated by light of wavelength $\lambda$,the stopping potential for the photoelectric current is $3 \text{ V}$. When the same surface is illuminated by light of wavelength $2 \lambda$,the stopping potential is $1 \text{ V}$. The threshold wavelength for this surface is: