Describe photoelectric effect and state the laws of photoelectric emission.

Explanation

Photoelectric effect is the phenomenon of emission of electrons by certain substances when they are illuminated by radiations like X-rays, ultra-violet rays and even visible light. The substances (mainly alkali metals) which emit photoelectrons are called photosensitive substances.

Experimental studies. It consists of an evacuated tube enclosing a plate P coated with photosensitive substances. Plate Q can be given any positive, negative or zero potential with the help of a potential dividing arrangement as shown in the figure. Here `muA` is microammeter to note the current.