Explain with reason: Green light emit electron from certain metal surface while yellow light does not

Explain with reason: When the wavelength of incident light is decreased, the velocity of emitted photo elec trons increases

The de-Broglie wavelength of the electron when it is emitted from the metal surface will be: Provided that the stopping potential of the electrons emitted in a photoelectric experiment is V.

Electrons are emitted with zero velocity from a metal surface when it is exposed to radiation of wavelength 6800 overset@A . Calculate the threshold frequency (v_0) and work function (w_0) of the metal.