Electromagnetic Waves

PHYS 2426 Engineering Physics II Problem 33.2 1. The sun radiates electromagnetic energy equally in all directions. The amount of this radiant energy which reaches the surface of the earth is approximately 1000 W/m. This quantity is called the solar constant. (a) Knowing that the average distance from the sun to the earth is 1.50 x 101 m, calculate the power of the sun. (b) Calculate the electromagnetic energy density. This is the amount of energy contained in one cubic meter of space outside. (c) Use the answer of part (b) to calculate the maximum electric and magnetic fields of the sun's light. (d) Assuming 50% absorption of sun light energy by the skin, how much energy is absorbed by your face if you lay out in the sun one hour? The average area of a person's face is approximately 0.020 mPHYS 2426 Engineering Physics II Problem 33.3 1. The laser (Light Amplification for Stimulated Emission of Radiation) has special properties which makes it a convenient research tool. It is presently used extensively in medical applications. The two most important special properties are: (1) It is a single frequency light source (approximately) and (2) It is emitted as a collimated beam in a certain direction as opposed to light from a light bulb which is emitted in all directions. This allows for large light intensity even from low power lasers. The helium-neon laser you will use in experiment (11) has a power rating of 0.5 m W. (a) How much energy is contained in a 2.5 m length of the beam. Assume the beam is cylindrical and of constant cross section. (b) Calculate the intensity of the laser light at a distance of 2.5m from the laser if the beam cross section has a diameter of 2.00 mm = 0.002 m.