Do all the electrons that absorb a photon come out as photoelectrons?

Radiation of wavelength 5000 oversetcircA and of intensity 2xx10^-3w cm^-2 falls on a photosensitive surface. Assuming that every absorbed photon results in the ejection of photoelectron, find how many photoelectrons are produced per cm^2 per sec.

An n-type semiconductor is the one which has excess of free electrons and p-type semiconductor is deficient in these. When a p-n junction is formed, the electrons should flow from n to p region. But all the electrons do not do so. Explain, why.

Calculate the threshold wavelength of photons, which can emit photoelectrons from cesium. Given that work function of cesium=1.8 eV.

Can a hydrogen atom absorb a photon whose energy exceeds its energy?

Do all the stars in the sky move ? Explain.

A hydrogen atom initially in the ground level absorbs a photon, which excites it to the n = 4 level. Determine the wavelength and frequency of photon.