The number of photons falling per second on a | vedclass

Name: Exam Paper Generator | JEE NEET Paper Generator | Vedclass
Brand: Vedclass
Rating: 5 (35 reviews)

Question

(B) The force exerted by a beam of photons on a perfectly absorbing surface is given by $F = \frac{P}{c}$,where $P$ is the power of the light beam and

Vedclass · Accepted Answer

$05$

Vedclass · Answer

(B) The force exerted by a beam of photons on a perfectly absorbing surface is given by $F = \frac{P}{c}$,where $P$ is the power of the light beam and $c$ is the speed of light.The power $P$ is given by $P = n \cdot E_{photon} = n \cdot \frac{hc}{\lambda}$,where $n$ is the number of photons per second.Substituting $P$ into the force equation: $F = \frac{n \cdot hc}{\lambda \cdot c} = \frac{n \cdot h}{\lambda}$.Rearranging to solve for $n$: $n = \frac{F \cdot \lambda}{h}$.Given $F = 6.62 	imes 10^{-5} \ N$,$\lambda = 5 	imes 10^{-7} \ m$,and $h = 6.62 	imes 10^{-34} \ J \cdot s$.$n = \frac{(6.62 	imes 10^{-5}) 	imes (5 	imes 10^{-7})}{6.62 	imes 10^{-34}}$.$n = \frac{6.62}{6.62} 	imes 5 	imes 10^{-5-7+34} = 1 	imes 5 	imes 10^{22} = 5 	imes 10^{22}$.Thus,$n = 5$.

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

Similar Questions

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 $............ \, J$.

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

$A$ light bulb of power $100 \ W$ is placed at the centre of a hollow sphere of radius $10 \ cm$. If $66\%$ of the energy is converted into light,then the pressure exerted by the light on the surface of the sphere will be (Assume the surface of the sphere to be perfectly absorbing).

Light is incident normally on a completely absorbing surface with an energy flux of $25\,W\,cm^{-2}.$ If the surface has an area of $25\,cm^2,$ the maximum momentum transferred to the surface in $40\,min$ time duration will be

$A$ parallel beam of light is incident normally on a plane surface absorbing $50\%$ of the light and reflecting the rest. If the incident beam carries $90 \text{ W}$ of power,the force exerted by it on the surface is ($C = 3 \times 10^8 \text{ m/s}$ is the velocity of light in air).

Vedclass Test Series

Exam Paper Generator

Online Exam Module