Calculate the frequency if the wavelength is $750 \ nm$.

The $Cs^+$ ion imparts a violet color to the flame. How is this related to the emitted radiation?

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

Explain the reason for the formation of a spectrum.

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

The energy of one mole of photons of radiation of frequency $2 \times 10^{12} \ Hz$ in $J \ mol^{-1}$ is $.....$ (Nearest integer) (Given: $h = 6.626 \times 10^{-34} \ Js$,$N_A = 6.022 \times 10^{23} \ mol^{-1}$)