There are two sources of light,each emitting with a power of $100 \, W$. One emits $X$-rays of wavelength $1 \, nm$ and the other visible light at $500 \, nm$. Find the ratio of the number of photons of $X$-rays to the photons of visible light of the given wavelength.

The relationship between the velocity and frequency of a photon in a vacuum is represented by a ...... .

The antiparticle of an electron is:

$A$ photon has a wavelength of $3 \,nm$. Its momentum and energy, respectively, will be:
$[h = 6.63 \times 10^{-34} \,Js, c = 3 \times 10^8 \,m/s]$

The number of photons emitted per second from a $60 \ W$ light bulb is .......... . The wavelength of the photon is $660 \ nm$. $(h = 6.6 \times 10^{-34} \ J \cdot s)$

The radiant energy from the Sun incident on the Earth's surface is $2 \ cal/cm^2 \cdot min$. If the average wavelength of solar radiation is $5500 \ \mathring A$,then the number of photons incident per minute on a surface area of $1 \ cm^2$ on the Earth's surface is ............ $(h = 6.6 \times 10^{-34} \ J \cdot s, 1 \ cal = 4.2 \ J)$