Exercise 32.28 A laser beam has diameter 1.30 mm . The beam exerts a force of 4.
ID: 1511167 • Letter: E
Question
Exercise 32.28
A laser beam has diameter 1.30 mm . The beam exerts a force of 4.0×109 N on a totally reflecting surface.
What is the amplitude of the electric field of the electromagnetic radiation in this beam?
Express your answer with the appropriate units.
Emax =
Exercise 32.28
A laser beam has diameter 1.30 mm . The beam exerts a force of 4.0×109 N on a totally reflecting surface.
What is the amplitude of the electric field of the electromagnetic radiation in this beam?
Express your answer with the appropriate units.
Emax =
Explanation / Answer
radiation pressure for total reflection
Pr = 2I/c
Pressure P = Force/area
F = Pr A
F = 2IA/C
Intensity I = F C /2A
Area A = pi r^2
r = D/2 = 1.3/2 = 0.65 mm
I = (4*10^-9 * 3*10^8)/(2 * pi * 0.00065^2)
I = 4.52 *10^5 W/m^2
also Intemsity I = Emax^2/2uoC
Emax^2 = 2 uo C I
Emax^2 = 2* 4pi *10^-7 * 3*10^8 * 4.52 *10^5
Emax = 1.84 *10^4 V/m is the electric field
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