If a source of $4 \ kW$ power emits $10^{20}$ photons/second,then this radiation belongs to which part of the electromagnetic spectrum?

Which of the following electromagnetic waves has the lowest frequency?

The correct match between the entries in column $I$ and column $II$ is:
$I$ (Radiation) | $II$ (Wavelength)
$(a)$ Microwave | $(i)$ $100 \, m$
$(b)$ Gamma rays | $(ii)$ $10^{-15} \, m$
$(c)$ $A.M.$ radio waves | $(iii)$ $10^{-10} \, m$
$(d)$ $X$-rays | $(iv)$ $10^{-3} \, m$

Match the following types of waves with their wavelength ranges:

$i$. Microwave	$(a)$. $700 \ nm$ to $400 \ nm$
$ii$. Visible light	$(b)$. $1 \ nm$ to $10^{-3} \ nm$
$iii$. Ultraviolet	$(c)$. $0.1 \ m$ to $1 \ mm$
$iv$. $X$-rays	$(d)$. $400 \ nm$ to $1 \ nm$

The wavelength $21 \ cm$ emitted by atomic hydrogen in interstellar space belongs to

Practically,the ozone layer absorbs radiations of wavelength: