The metal used for making radiation shield is

Give the characteristics of electromagnetic radiation. Give the relation between them.

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.

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

The photoelectric effect demonstrates:

$750$ waves of an electromagnetic radiation pass a point in one minute. What is the wavelength of the radiation?