What is Maxwell's electromagnetic theory?

$750$ waves of an energy radiation pass in one minute from a point. What will be the wavelength of the radiation? (Assume the speed of radiation is $3 \times 10^8 \ m/s$)

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.

The energy of an electromagnetic radiation is $19.875 \times 10^{-13} \ erg$. What is its wave number in $cm^{-1}$? $(h = 6.625 \times 10^{-27} \ erg \ sec, c = 3 \times 10^{10} \ cm \ sec^{-1})$

The wavelength of photon $A$ is $400 \ nm$. The frequency of photon $B$ is $10^{16} \ s^{-1}$. The wave number of photon $C$ is $10^{4} \ cm^{-1}$. The correct order of energy of these photons is:

The Vijayawada $FM$ radio station broadcasts at a frequency of $103.4 \ MHz$. The wavelength of the corresponding radio waves (in $m$) is