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

Explain the properties of electromagnetic waves.

The work function $(\phi)$ of some metals is listed below. The number of metals which will show photoelectric effect when light of $300 \ nm$ wavelength falls on the metal is

Metal	$Li, Na, K, Mg, Cu, Ag, Fe, Pt, W$
$\phi \ (eV)$	$2.4, 2.3, 2.2, 3.7, 4.8, 4.3, 4.7, 6.3, 4.75$

What is an emission spectrum?

Describe the electromagnetic spectrum.

Which emission transition series is obtained when an electron jumps from $n_2 = \infty$ to $n_1 = 1$?