Question

write short note on ;1.photoelectric effect

Answer 1

The photoelectric effect physically meansk light incidents on a matel,electron is ejected with certain kinetic energy.How this is explained?.The explanaition is:incident light is made of quanta(photons) each with quantized energy E=hf,where h is Planck constant=6.63X10^-34 J.sec.and f is the frequency of the wave associated with the photon.If E is enough to overcom the work function of the metal w,the work binding the electron into the metal,which is a characteristic to each known metal,with remaining energy for the electron as kinetic energy,then the electron will ejected with a kinetic energy given by,K.E=hf-w.
So you see the energy depends on the frequency(f) not on the intensity.

Answer 2

The photoelectric effect or photoemission is the emission of electrons or other free carriers when light is shone onto a material. Electrons emitted in this manner can be called photoelectrons. The phenomenon is commonly studied in electronic physics, as well as in fields of chemistry, such as quantum chemistry or electrochemistry.

According to classical electromagnetic theory, this effect can be attributed to the transfer of energy from the light to an electron. From this perspective, an alteration in the intensity of light would induce changes in the rate of emission of electrons from the metal. Furthermore, according to this theory, a sufficiently dim light would be expected to show a time lag between the initial shining of its light and the subsequent emission of an electron. However, the experimental results did not correlate with either of the two predictions made by classical theory.