27-1. A laser produces a monochromic beam of electromagnetic waves with a wavelength of 560 nm {1720 nm} which is traveling straight up {due east}. After passing through a polarizing filter the beam emerges as an electromagnetic plane wave with the E-field oscillating in the north-south vertical plane {horizontal plane} and having an amplitude of 24.0 V/cm {17.0 kV/m}.

(A) What is the frequency with which the EM-waves oscillate? In which region of the electromagnetic spectrum does this laser radiate? Ans:{1.74x10¹⁴ Hz, infrared}

(B) What is the magnitude of the amplitude of the B-field and in which plane does it oscillate? Ans:{56.7 mT, E-W vertical plane}

(C) What is the intensity of the EM-radiation of this beam? Ans:{383 kW/m²}

(D) What is average energy per unit volume of the EM-radiation in this beam? Ans:{1.28 mJ/m³ = 1.28 kJ/cm³}

BONUS:
27-2. On a "clear day" the intensity of solar radiation reaching the Earth's surface is 1.20 kW/m² {1.15 kW/m²}. Determine the maximum value of the electric and magnetic field at the Earth's surface due to solar radiation. Ans:{931 V/m, 3.10 mT}

Assignment #28

Section 32-3

Not Required this Quarter

28-1. A 250 W {75.0 W} light bulb produces a spherically symmetric EM-waves.

(A) What is the intensity of the light 3.90 m from the bulb? Ans:{392 mW/m²}

(B) What pressure would the light produce on a small piece of paper perpendicular to the emerging light if all the light striking the paper is absorbed {reflected}? Ans:{2.62 nPa}

28-2. A cylindrical glass bead with a height of .750 mm {1.80 mm}, a radius of 1.50 mm {2.10 mm}, and a density of 2.60 gm/cm³ is suspended in "mid-air" by a laser that is directed upwards towards the flat bottom of the bead.

(A) Determine the light pressure on the bottom of the bead to just suspend the bead if the bottom of the bead was black so that it acted like a perfect absorber {was a mirror so that it acted like a perfect reflector). Ans:{45.9 Pa}

(B) Determine the power output of laser beam need to just suspend the bead if the bottom of the bead was black so that it acted like a perfect absorber {was a mirror so that it acted like a perfect reflector). Ans:{95.3 kW}