An astronaut floating freely in space decides to use his flash light as a rocket. He shines a $10$ watt light beam in a fixed direction so that he acquires momentum in the opposite direction. If his mass is $80$ kg, how long must he need to reach a velocity of $1$ $ms^{-1}$

The spectrum of radiation $1.0 \times {10^{14}}Hz$ is in the infrared region. The energy of one photon of this in joules will be

A photon of wavelength $6630 \  Å$ is incident on a totally reflecting surface. The momentum delivered by the photon is equal to

The energy equivalent to $1\,mg$ of matter in $MeV$ is

Energy of a quanta of frequency ${10^{15}}Hz$ and $h = 6.6 \times {10^{ – 34}}J{\rm{ – }}\sec $ will be