Light with an energy flux of $18 \; W/cm^2$ falls on a non-reflecting surface at normal incidence. If the surface has an area of $20 \; cm^2$,find the average force exerted on the surface during a $30$ minute time span.

The force on a hemisphere of radius $1\, cm$ if a parallel beam of monochromatic light of wavelength $500\, nm$ falls on it with an intensity of $0.5\, W/cm^2$,striking the curved surface in a direction which is perpendicular to the flat face of the hemisphere is (assume the collisions to be perfectly inelastic).

$A$ 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:

Light with an energy flux of $25 \times 10^4 \, W/m^2$ falls on a perfectly reflecting surface at normal incidence. If the surface area is $15 \, cm^2$,the average force exerted on the surface is:

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)

Electromagnetic waves of energy flux $75 \times 10^4 \ W m^{-2}$ are incident normally on a surface of area $40 \ cm^2$. If the surface absorbs the flux completely,the total momentum delivered to the surface in one second is: