Can we use any substance as photoelectron emitter?

Can a substance contract on heating?

Given instructions same as in chapter 1. Assertion: Any substance can be used for the emission of photoelectrons. Reason: Radiations of suitalbe frequency (more than threshold frequency) should be available.

Light of wavelength 488 nm is produced by an argon laser which is used in the photoelectric effect. When light from this spectral line is incident on the emitter, the stopping (cut off) potential of photoelectrons is 0.38 V. find the work function of the material from whih the emitter is made.

Tanquillizers are substances used for the treatment of