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

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

The number of the following statements which is/are incorrect is:
$A$. Line emission spectra are used to study the electronic structure.
$B$. The emission spectra of atoms in the gas phase show a continuous spread of wavelength from red to violet.
$C$. An absorption spectrum is like the photographic negative of an emission spectrum.
$D$. The element helium was discovered in the sun by spectroscopic method.

Calculate the wavelength of yellow light having a frequency of $5.09 \times 10^{14} \ Hz$.

It is observed that characteristic $X$-ray spectra of elements show regularity. When frequency to the power '$n$' i.e.,$v^{n}$ of $X$-rays emitted is plotted against atomic number '$Z$',the following graph is obtained. The value of '$n$' is

What are the different regions of the electromagnetic spectrum?