Homework Assignment #4


Section number

Date Due: Oct. 6

1. Suppose you are operating a remotely-controlled spacecraft on Venus from a station on Earth. How long will it take a radio signal to travel from Earth to Venus, if the two planets are nearest each other in their (assumed circular) orbits?

2. Arrange the following kinds of electromagnetic radiation in order from most to least energetic (shortest to longest wavelength): ultraviolet, radio, infrared, X-ray.

3. Imagine that you are going before a federal government committee to justify the expense of putting a large telescope in space. What arguments could you use to try and persuade the skeptical committee?

4. Using Wien's Law, determine the wavelength and corresponding kind of radiation emitted by (a) a "brown-dwarf" star with T = 1000 K; (b) a blue supergiant star with T = 30,000 K.

5. A commercial Schmidt-Cassegrain telescope has an effective focal length of 200 cm and an f-ratio of 10.

(a) What is the telescope's aperture in cm?

(b) The human eye has a maximum pupil diameter of 0.8 cm. What is the ratio of light gathering power of the telescope and the human eye?

(c) The telescope is used in conjunction with a 1.5 cm focal length eyepiece. What is the telescope's magnification?

(d) Calculate the telescope's theoretical resolving power a, in arc-seconds, if the wavelength l = 500 nm.