$A$ radiation of energy $E$ falls normally on a perfectly reflecting surface. The momentum transferred to the surface is ($c$ is velocity of light).

If $2.5 \times 10^{-6} \ N$ average force is exerted by a light wave on a non-reflecting surface of $30 \ cm^{2}$ area during $40$ minutes of time span,the energy flux of light just before it falls on the surface is .................. $W/cm^{2}$. (Round off to the Nearest Integer) (Assume complete absorption and normal incidence conditions are there)

$A$ beam of light with intensity $10^{-3} \text{ W m}^{-2}$ and cross-sectional area $20 \text{ cm}^2$ is incident on a fully reflective surface at an angle of $45^{\circ}$. The force exerted by the beam on the surface is:

$A$ small mirror of mass $m$ is suspended by a massless thread of length $l$. Find the small angle through which the thread will be deflected when a short pulse of laser of energy $E$ falls normally on the mirror. ($c=$ speed of light in vacuum and $g=$ acceleration due to gravity)

Radiations of intensity $0.5 \ Wm^{-2}$ are striking a metal plate. The pressure exerted on the plate is:

$A$ small object at rest absorbs a light pulse of power $20\,mW$ and duration $300\,ns$. Assuming the speed of light as $3 \times 10^8\,m/s$,the momentum of the object becomes equal to $.........\times 10^{-17}\,kg\,m/s$.