$A$ flashlight of intensity $9 \, W/cm^2$ illuminates a perfectly reflective surface of area $300 \, cm^2$. The average force exerted on the surface due to the incident light photons is

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

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 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: $h = 6.62 \times 10^{-34} \ J \cdot s$)

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:

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A)$: The electromagnetic wave exerts pressure on the surface on which they are allowed to fall.
Reason $(R)$: There is no mass associated with the electromagnetic waves.
In the light of the above statements, choose the correct answer from the options given below: