The number of photons falling per second on a completely darkened plate to produce a force of $6.62 \times 10^{-5} \ N$ is $n$. If the wavelength of the light falling is $5 \times 10^{-7} \ m$,then $n = \_ \times 10^{22}$. (Given: $h = 6.62 \times 10^{-34} \ J \cdot s$)

$50\, W/m^2$ energy density of sunlight is normally incident on the surface of a solar panel. Some part of incident energy $(25\%)$ is reflected from the surface and the rest is absorbed. The force exerted on $1\, m^2$ surface area will be close to $(c = 3 \times 10^8\, m/s)$.

$A$ 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:

$A$ beam of white light is incident normally on a plane surface absorbing $70\%$ of the light and reflecting the rest. If the incident beam carries $10\,W$ of power,find the force exerted by it on the surface :-

$A$ point source of light is placed at the centre of curvature of a hemispherical surface. The source emits a power of $24 \, W$. The radius of curvature of the hemisphere is $10 \, cm$ and the inner surface is completely reflecting. The force on the hemisphere due to the light falling on it is $.......... \times 10^{-8} \, N$.

$A$ 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 $c$.)