Light with an average flux of $20 \, W/cm^2$ falls on a non-reflecting surface at normal incidence having a surface area of $20 \, cm^2$. The energy received by the surface during a time span of $1 \, minute$ is $............ \, J$.

$A$ parallel beam of monochromatic light of frequency $\nu$ is incident on a surface. The intensity of the beam is $I$ and the area of the surface is $A$. Find the force exerted by the light beam on the surface if it is perfectly reflecting and the light beam is incident at an angle of incidence $\theta$. (The speed of light is denoted as $c$.)

Find the compression in the spring with spring constant $K = 5 \ N/m$ which is attached to a metal plate of area $50 \ m^2$. Light of intensity $I = 40 \ MW/m^2$ is incident at an angle of $60^o$ on the metal plate,and the coefficient of reflection is $\rho = 0.5$ for the plate. (in $m$)

Which of the following is an incorrect statement regarding a photon?

An electromagnetic wave of intensity $1400 \, W/m^2$ falls on a metal surface of area $1.5 \, m^2$ and is completely absorbed by it. Find the force exerted by the beam.

$A$ $1.5 \,kW$ laser beam of wavelength $6400 \,\mathring A$ is used to levitate a thin aluminium disc of the same area as the cross-section of the beam. The laser light is reflected by the aluminium disc without any absorption. The mass of the foil is close to ......... $kg$.