The GPS network consists of 24 satellites, each of which makes two orbits around the earth per day. Each satellite transmits a 50.0 (or even less) sinusoidal electromagnetic signal at two frequencies, one of which is 1575.42 . Assume that a satellite transmits half of its power at each frequency and that the waves travel uniformly in a downward hemisphere.

A)What average intensity does a GPS receiver on the ground, directly below the satellite, receive? (Hint: First use Newton's laws to find the altitude of the satellite.)
B)What is the amplitude of the electric field at the GPS receiver in part (a)?
C)What is the amplitude of the magnetic field at the GPS receiver in part (a)?
D)How long does it take the signal to reach the receiver?
E)If the receiver is a square panel 2.00 on a side that absorbs all of the beam, what average pressure does the signal exert on it?
F)What wavelength must the receiver be tuned to?

How is the gravitational force related to the distance between two objects?

Some material consisting of a collection of microscopic objects is kept at a high temperature. a photon detector capable of detecting photon energies from infrared through ultraviolet observes photons emitted with energies of 0.3 ev, 0.5 ev, 0.8 ev, 2.0ev, 2.5ev, and 2.8ev. these are the only photon energies observed. (a) draw and label a possible energy-level diagram for one of the microscopic objects, which has four bound states. on the diagram, indicate the transitions corresponding to the emitted photons. explain briefly. (b) would a spring–mass model be a good model for these microscopic objects? why or why not? (c) the material is now cooled down to a very low temperature, and the photon detector stops detecting photon emissions. next, a beam of light with a continuous range of energies from infrared through ultraviolet shines on the material, and the photon detector observes the beam of light after it passes through the material. what photon energies in this beam of light are observed to be significantly reduced in intensity (“dark absorption lines”)? explain briefly.

What does si stand for, when referring to a system of measurement