Explorations: An Introduction to Astronomy (Arny), 7th Edition

Chapter 5: Telescopes

Problems

1
Compare the light-gathering power of a telescope with a 10-centimeter (about 4-inch) diameter mirror to that of the human eye. (Take the diameter of the pupil of the eye to be about 5 millimeters.)
2
Estimate your eye's resolving power by drawing two lines 1 millimeter apart on a piece of paper. Put the paper on the wall and then step back until the two lines appear as one, measuring that distance. From the distance and the separation of the lines (1 millimeter), estimate their angular separation. How does your result for the eye's resolving power compare with that calculated from the resolving-power formula, using a pupil diameter of 5 millimeters and a wavelength of 500 nanometers?
3
Can the unaided human eye resolve a crater on the Moon whose angular diameter is 2 minutes of arc (= 120 seconds of arc)? (Take the diameter of the pupil of the eye to be about 5 millimeters and the wavelength of the light to be 500 nanometers.)
4
Determine the resolving power of a 25-meter radio telescope observing 10-centimeter radio waves. Compare this to its resolving power for 1-meter radio waves. (Remember to convert units for the equation in section 5.2.)
5
Using ratios or proportionalities, determine how large a diameter "eye" a person would need to see as well (1) in the infrared at wavelength of 12 micrometers, and (2) in the radio at a wavelength of 10 centimeters, as we can in the visible at 500 nanometers with a 5-millimeter pupil.
6
Compute the collecting area of the 27 telescopes in the Very Large Array radio interferometer if each has a diameter of 25 meters. If this were the collecting area of a single dish, what would be its diameter?
7
If a CCD could record 80% of the photons striking it, and a photograph about 4%, how many times larger in diameter would a telescope have to be, to take a photograph equal in sensitivity to a CCD image in the same amount of time?
8
The altitude of Hubble's orbit is about 569 km above the surface of the Earth. Calculate the circumference of the orbit, the orbital velocity, and the period of the orbit (see section 3.6). How does this period affect observations?
Glencoe Online Learning CenterScience HomeProduct InfoSite MapContact Us

The McGraw-Hill CompaniesGlencoe

Please read our Terms of Use and Privacy Notice before you explore our Web site. To report a technical problem with this Web site, please contact the Web Producer.