What is the frequency of violet light having wavelength $400 \ nm$?

Arrange the following types of radiation in increasing order of frequency:
$(a)$ radiation from microwave oven
$(b)$ amber light from traffic signal
$(c)$ radiation from $FM$ radio
$(d)$ cosmic rays from outer space
$(e)$ $X$-rays

Calculate the frequency in $Hz$ of orange colour light having wavelength $600 \ nm$. $[c = 3 \times 10^8 \ ms^{-1}]$

$A$ hypothetical electromagnetic wave is shown in the figure. Find out the wavelength of the radiation.

The charge on gamma rays is

The electron is