Advertisements
Advertisements
Question
Show that the radiation pressure exerted by an EM wave of intensity I on a surface kept in vacuum is I/c.
Solution
Let us consider a surface exposed to electromagnetic radiation. The radiation is falling normally on the surface. Further, intensity of radiation is I and area of surface exposed to radiation is A.
E = Energy received by surface per second = I.A
N = Number of photons received by surface per second
N = `E/E_("photon") = (Eλ)/(hc) = (IAλ)/(hc)`
Let the surface is perfectly absorbing, `ΔP_("one photon") = h/λ`
⇒ F = `N xx ΔP_("one photon") = (IA)/c`
Also, Pressure P = `F/A = I/c`
APPEARS IN
RELATED QUESTIONS
The amplitude of the magnetic field part of a harmonic electromagnetic wave in vacuum is B0 = 510 nT. What is the amplitude of the electric field part of the wave?
Which segment of electromagnetic waves has highest frequency? How are these waves produced? Give one use of these waves.
Why is the amount of the momentum transferred by the em waves incident on the surface so small ?
How does a charge q oscillating at certain frequency produce electromagnetic waves?
Sketch a schematic diagram depicting electric and magnetic fields for an electromagnetic wave propagating along the Z-direction.
State any one property which is common to all electromagnetic waves.
What is displacement current?
Let an electromagnetic wave propagate along the x-direction, the magnetic field oscillates at a frequency of 1010 Hz and has an amplitude of 10-5 T, acting along the y – direction. Then, compute the wavelength of the wave. Also write down the expression for the electric field in this case.
An accelerate electron would produce.
Light with an energy flux of 20 W/cm2 falls on a non-reflecting surface at normal incidence. If the surface has an area of 30 cm2 the total momentum delivered (for complete absorption) during 30 minutes is ______.
A plane electromagnetic wave of frequency 500 MHz is travelling in a vacuum along a y-direction.
At a particular point in space and time, `vec"B"` = 8.0 × 10-8 `hat"Z"`T. The value of the electric field at this point is ______.
(speed of light = 3 × 108 ms-1)
`hat x, hat y, hat z` are unit vectors along x, y, and Z directions.
