What should be the velocity of an electron so that its momentum becomes equal to that of a photon of wavelength $5200 \, \mathring{A}$? (Given: $h = 6.63 \times 10^{-34} \, J \cdot s$, $m_e = 9.1 \times 10^{-31} \, kg$)

$A$ scientist claims to have a perfect technique in which he can spontaneously convert an electron completely into energy in the laboratory without any other material required. What is the conclusion about this claim from our current understanding of physics?

Can a quantum of light be associated with a particle?

The momentum of a photon in an $X-$ray beam of $10^{-10} \ m$ wavelength is

Energy of a photon whose frequency is $10^{12} \text{ MHz}$ is
[ Planck's constant,$h = 6.63 \times 10^{-34} \text{ Js}, e = 1.6 \times 10^{-19} \text{ C}$ ]

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 ............ $(h = 6.6 \times 10^{-34} \ J \cdot s, 1 \ cal = 4.2 \ J)$