$A$ metal surface emits photoelectrons when the incident radiation possesses a minimum.....

Electromagnetic radiation with maximum wavelength is

The energy of one mole of photons of radiation whose frequency is $5 \times 10^{10} \, s^{-1}$ is .......... $J$.

What is the frequency of violet light having wavelength $400 \ nm$?

The ....... series is observed in the visible region of the hydrogen spectrum.

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