Identify the region of the electromagnetic spectrum for the spectral lines when electron transition takes place from higher energy levels to $n=3, 4, 5$ in the atomic spectrum of hydrogen.

Between a photon of violet light with a wavelength of $4000 \ \mathop A\limits^o$ and a photon of red light with a wavelength of $7000 \ \mathop A\limits^o$,which one has higher energy?

Calculate the energy of one mole of photons of radiation whose frequency is $5 \times 10^{14} \ Hz$.

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

Arrange the following types of radiation in increasing order of frequency:
$(a)$ radiation from microwave oven
$(b)$ amber light from traffic signal
$(c)$ radiation from $FM$ radio
$(d)$ cosmic rays from outer space
$(e)$ $X$-rays

Work function $(W_0)$ values of six metals (in $eV$) are given below: $Li: 2.42, Mg: 3.7, Cu: 4.8, Ag: 4.3, K: 2.25, Na: 2.3$. How many of the above metals do not eject the electrons when they are made to strike with radiation of wavelength $400 \text{ nm}$? $(h = 6.62 \times 10^{-34} \text{ Js})$