At one instant, the electric and magnetic fields at one point of an electromagnetic wave are and .
a. What are the values of and ?
b. What is the Poynting vector at this time and position?
(a) The values of and
(b) The Poynting vector at time and position is
The Poynting vector is:
Large quantities of dust should have been left behind after the creation of the solar system. Larger dust particles, comparable in size to soot and sand grains, are common. They create shooting stars when they collide with the earth's atmosphere. But very small dust particles are conspicuously absent. Astronomers believe that the very small dust particles have been blown out of the solar system by the sun. By comparing the forces on dust particles, determine the diameter of the smallest dust particles that can remain in the solar system over long periods of time. Assume that the dust particles are spherical, black, and have a density of . The sun emits electromagnetic radiation with power .
A laser pulse is focused with a lens to a diameter of .
a. What is the laser beam’s electric field amplitude at the focal point?
b. What is the ratio of the laser beam’s electric field to the electric field that keeps the electron bound to the proton of a hydrogen atom? The radius of the electron orbit is .
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