Is the ratio of frequencies of ultraviolet rays and infrared rays in glass more than, less than or equal to 1?

Write four uses of ultraviolet rays.

What is the ratio of speed of infrared rays and ultraviolet rays in vacuum?

Is the ratio of number of holes and the number of conduction electrons in an n-type extrinsic semiconductor more than,less than or equal to 1 ?

Give two properties and four uses of ultraviolet rays?