Choose all that apply. Refraction telescopes: are used to pick up the faintest objects in the sky
have small lengths compared to other telescopes
are used when image quality is important
require less maintenance
are used by professional astronomers

What do radio waves and microwaves have in common? both are at the side of the spectrum that has the shortest wavelengths. both are at the side of the spectrum that has the lowest radiant energy. both are at the side of the spectrum that has the lowest frequency. both are found next to visible light on the electromagnetic spectrum.

1point) a skydiver weighing 130 lb (including equipment) falls vertically downward from an altitude of 14,000 ft and opens the parachute after 20 s of free fall. assume that the force of air resistance, which is directed opposite to the velocity, is of magnitude 0.85|v|0.85|v| when the parachute is closed and is of magnitude 17|v|17|v| when the parachute is open, where the velocity vv is measured in ft/s. assume that acceleration due to gravity has magnitude 32 ft/s/s; remember that weight is the product of mass and gravitational acceleration. find the speed of the skydiver when the parachute opens. speed is 150.6121788 ft/s find the skydiver's height when the parachute opens. height is 2338.98591 ft find the limiting velocity vlvl after the parachute opens. (think about whether this should be positive or negative.) vl=vl= 7.647 ft/s

If it takes a planet 2.8 x 10^8 s to orbit a star with a mass of 6.2 x 10^30 kg what is the average distance between the planet and the star