What protects us from $UV$ light emitted by the Sun?

What is the use or importance of the ozone layer?

Match the List-$I$ (Phenomenon associated with electromagnetic radiation) with List-$II$ (Part of electromagnetic spectrum) and select the correct code from the choices given below:

List-$I$	List-$II$
$I$. Doublet of sodium	$A$. Visible radiation
$II$. Wavelength corresponding to temperature associated with the isotropic radiation filling all space	$B$. Microwave
$III$. Wavelength emitted by atomic hydrogen in interstellar space	$C$. Short radio wave
$IV$. Wavelength of radiation arising from two close energy levels in hydrogen	$D$. $X$-rays

Which of the following is responsible for the greenhouse effect?

Photons of an electromagnetic radiation have an energy of $11 \, keV$ each. To which region of the electromagnetic spectrum does it belong?

Which of the following radiations has the shortest wavelength?