Find the wavelength of radiation having frequency $4 \times 10^{11} \ kHz$.

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

Find the ratio of energy for radiations having $6000 \ \mathring{A}$ and $4000 \ \mathring{A}$ wavelength.
$(h = 6.62 \times 10^{-34} \ J \ s, c = 3 \times 10^8 \ m \ s^{-1})$

Electromagnetic radiation of wavelength $663 \ nm$ is just sufficient to ionise the atom of metal $A.$ The ionization energy of metal $A$ in $kJ \ mol^{-1}$ is ...... .
(Rounded-off to the nearest integer) $\left[ h = 6.63 \times 10^{-34} \ Js, c = 3.00 \times 10^{8} \ ms^{-1}, N_{A} = 6.02 \times 10^{23} \ mol^{-1} \right]$

If the energies of two photons are in the ratio of $3:2$,their wavelengths will be in the ratio of

Which of the following sets of radiations cannot be seen in the hydrogen atomic spectrum? $(i)$ $\gamma$-radiation $(ii)$ $UV$ $(iii)$ $X$-rays $(iv)$ Infrared