The position vector x for an electron moving with velocity much less than c in a plane monochromatic wave epsilon e_0 cos(omega t - kz) is determined by the equation of motion md^2 x/dt^2 = e epsilon e_0 cis (omega t - kz). show that the refractive index of an electron gas is given by eq. (3.14.13). assume that in the ionosphere the refractive index for 100-mhz radio waves is 0.90 and that the free electrons make the greatest contribution to the index. estimate the number density of electrons. why is the contribution of positively charged ions to the refractive index much smaller? choose an am and an fm radio station in your area and compare their frequencies to the plasma frequency of the ionosphere.

Marcella is a four-year-old girl who is a victim of emotional child abuse. based on the child and family services improvement and innovation act of 2011, which action should the government take for marcella? a. the state should arrest marcella’s abuser. b. the state should find a home for marcella as soon as possible. c. the state should enforce stricter laws in the area where marcella resides. d. the state should provide medical assistance to marcella.

At what time will the interfering waves have an amplitudeof zero?

To place a communications satellite into a geosynchronous orbit at an altitude of 22,240 mi above the surface of the earth, the satellite first is released from a space shuttle , which is in a circular orbit at an altitude of 185 mi, and then is propelled by an upper-stage booster to its final altitude. as the satellite passes through a, the booster's motor is fired to insert the satellite into an elliptic transfer orbit. the booster is again fired at b to insert the satellite into a geosynchronous orbit. knowing that the second firing increases the speed of the satellite by 4810ft/s, determine (a.) the speed of the satellite as it approaches b on the elliptic transfer orbit, (b.) the increase in speed resulting from the first firing at a.