Maxwell from his studies concluded that an electric field and a magnetic field changing with time in a direction perpendicular to each other produce a disturbance which propagates in a direction perpendicular to both the fields. This disturbance is called electromagnetic wave. The em wave is of transverse nature. The velocity of em wave in vacuum is `c=1/(sqrtmu_0in_0)` where `mu_0=` magnetic permeability of free space and `in_0` =electric permittivity of free space. The wavelength of e.m. wave varies over a wide range from `10^(-14)` to `10^3m`. The em wave of different wavelengths travel with same speed in vacuum but move with different speeds in any medium.
(i) What are the various e.m wave invisible to eye whose wavelength is lower than the smallest wavelength of visible light?
(ii) How do you conclude that white light travels in vacuum with a speed `3xx10^8ms^-1`?
(iii) What do you learn from the above study?

Explanation

(i) The invisible e.m. wave whose wavelength is less than the smallest wavelength of visible
light are ultraviolet radiations, x-rays and `gamma`-rays.
(ii) The white light is an e.m. wave. The speed of e.m. wave in vacuum is given by
`c=1/(sqrtmu_0in_0)`, where mu_0 =4pixx10^-7TmA^-1 and in_0=1/(4pixx9xx10^9)C^2N^-1m^-2`
`:. c=1/(sqrt((4pixx10^-7) 1/((4pixx9xx10^9))))=3xx10^8ms^-1`
(iii) From the above study, we find that nature/God that created all human beings alike. When they are exposed
to different environments of the world and family, their thinking/views/speeds become different. God
wants us to live in peace treating everyone as equal.