3. A laser uniformly illuminates an area with green light that has an average in

Question

3. A laser uniformly illuminates an area with green light that has an average intensity of 580 W/m2. What is the rms value of the magnetic field of this light? A) 0.23 × 10-5 T B) 1.13 x 106 T C) 1.56 x 10-6 T E) 1.66 x 106 T D) 1.74 × 10-6 T 4. An AM radio station broadcasts radio waves uniformly in all directions with a total average power of 100 kW. What is the maximum value of the electric field at a distance of 350 miles from the station transmitter antenna? (1 kW-1000 W, 1 mile-1 609 m) A) 8.2× 10-5 N/C B) 5.2 x 10-4 N/C C) 4.3 x 10-3 N/C D) 1.6 x 109 N/C E) zero tesla

Explanation / Answer

3) C)1.56*10^-6 T

Intensity of lasee light, I = Erms^2/(c*mue)

Erms = sqrt(I*c*mue)

= sqrt(580*3*10^8*4*pi*10^-7)

= 467.6 N/c

Brms = Erms/c

= 467.6/(3*10^8)

= 1.56*10^-6 T

4) C) 4.3*10^-3 N/c

Intensity = Power/Area

= P/(4*pi*r^2)

= 100*10^3/(4*pi*(350*1609)^2)

= 2.51*10^-8 W/m^2

Intensity of laser light, I = Emax^2/(2*c*mue)

Emax = sqrt(2*I*c*mue)

= sqrt(2*2.51*10^-8*3*10^8*4*pi*10^-7)

= 4.3*10^-3 N/c

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