Discuss the history of em waves brief.

What is the velocity of e.m. waves in free space?

Electromagnetic waves of frequency 5 xx 10^(14) Hz are passed through a liquid.The wavelength of the waves in liquid is measured to be 4.5 xx 10^(-7) m . Calculate velocity of e.m. waves in the liquid and

Discuss briefly the behaviour of earth's atmosphere towards the propagation of electromagnetic waves.

State the characteristics of e.m. waves.