$A$ photon of wavelength $6630 \mathring{A}$ is incident on a totally reflecting surface. The momentum delivered by the photon is equal to

Electromagnetic radiations of frequency $\nu$ consist of a stream of particles called photons. Which of the following statements is / are true about photons:

Wavenumber for a radiation having $5800 \ \mathring{A}$ wavelength is $x \times 10 \ cm^{-1}$. The value of $x$ is . . . . . . . .

What is the speed of all types of electromagnetic radiation in a vacuum? What is it called?

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 $cm^{-1}$? $(h = 6.625 \times 10^{-27} \ erg \ sec, c = 3 \times 10^{10} \ cm \ sec^{-1})$