In which type of radiation do the mass number and atomic number remain unchanged?

Chlorophyll present in green leaves of plants absorbs light at $4.620 \times 10^{14} \ Hz$. Calculate the wavelength of radiation in nanometer. Which part of the electromagnetic spectrum does it belong to?

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:

Calculate the energy per mole of photons of electromagnetic radiation having a wavelength of $700 \ nm$. $\left[h = 6.626 \times 10^{-34} \ J \ s, c = 3 \times 10^8 \ m/s, N_A = 6.022 \times 10^{23} \ mol^{-1}\right]$

Identify the correct statements from the following:
$I$) Isotopes of an element show different chemical behaviour
$II$) Lyman series of lines of hydrogen spectrum appear in $UV$ region
$III$) The oscillating electric and magnetic field components of electromagnetic radiation are perpendicular to each other and both are perpendicular to the direction of propagation of radiation

How is an electron observed? Explain.