The region in the electromagnetic spectrum where the Balmer series lines appear is

Mercury street lights emit light of a pale blue color with a wavelength of $436 \, nm$. Calculate its frequency.

When radiation of $300 \ nm$ is shone on five metals, namely $Li, Mg, Ag, Cu,$ and $K$, the number of metals that show the photoelectric effect is:

Consider a helium $(He)$ atom that absorbs a photon of wavelength $330 \ nm$. The change in the velocity (in $cm \ s^{-1}$) of the $He$ atom after the photon absorption is . . . . . .
(Assume: Momentum is conserved when the photon is absorbed. Use: Planck constant $= 6.6 \times 10^{-34} \ J \ s$,Avogadro number $= 6 \times 10^{23} \ mol^{-1}$,Molar mass of $He = 4 \ g \ mol^{-1}$)

Assertion : All photons possess the same amount of energy.
Reason : Energy of photon does not depend upon wavelength of light used.

What are the different regions of the electromagnetic spectrum?