A stationary particle of charge q = 3.0 10-8 C is placed in a laser beam (an ele

Question

A stationary particle of charge q = 3.0 10-8 C is placed in a laser beam (an electromagnetic wave) whose intensity is 2.0 103 W/m2. Determine the magnitudes of the (a) electric and (b) magnetic forces exerted on the charge. If the charge is moving at a speed of 3.7 104 m/s perpendicular to the magnetic field of the electromagnetic wave, find the magnitudes of the (c) electric and (d) magnetic forces exerted on the particle. For part A I have already tried 3.68 X 10^-5 and that is wrong. For part C I also tired 3.68 x 10^-5 and that is wrong. For part D I tried 4.18 x 10^9 and that is also wrong. Part B I got correct it is 0N.

Explanation / Answer

Given that,

q = 3*10^(-8) C

intensity l = 2*10^3 W/^2

(a)

we know that,

l = c*e0*E^2

E = sqrt (l / c*e0)

E = sqrt (2*10^3 / 3*10^8*8.85*10^(-12))

E = 868 N/C

electric force is,

Fe = q*E = 3*10^(-8) * 868

Fe = 2.6*10^(-5) N

(b)

l = B^2*c / u0

B = sqrt (u0*l / c)

B = sqrt (4*pi*10^(-7)*2*10^3 / 3*10^8)

B = 2.89*10^(-6) T

magnetic field is,

Fm = q*v*B = 0

(c)

if velocity of charge,

v = 3.7*10^4 m/s

Fe = 2.6*10^(-5) N

(d)

Fm = 3*10^(-8) * 3.7*10^4 * 2.89*10^(-6)

Fm = 32.12*10^(-10) T

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