Which of the following is $NOT$ a property of $X$-rays?

Write examples of a continuous spectrum.

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.

What is the charge on $\gamma$-rays?

The energies $E_1$ and $E_2$ of two radiations are $25 \ eV$ and $50 \ eV$ respectively. The relation between their wavelengths,i.e.,$\lambda_1$ and $\lambda_2$,will be:

The wavelength range of the visible spectrum extends from violet $(400 \, nm)$ to red $(750 \, nm).$ Express these wavelengths in frequencies $(Hz).$ $(1 \, nm = 10^{-9} \, m)$