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Astronomy Quiz 3
Midterm
| Question | Answer |
|---|---|
| The person who first showed that light is an electromagnetic wave was | James Clerk Maxwell in the 1860s. |
| The first person to prove that light did not travel at infinite speed was | Ole Rømer |
| Flash of light is transmitted through 2 parallel tubes of length 1 km, one evacuated, the other with water. Detectors sense the arrival times of the light flash at the ends of these tubes. What will be the relationship between arrival of these flashes? | The flash will arrive earliest through the evacuated tube |
| The frequency associated with blue light compared to the frequency of red light is | higher. |
| Suppose a light source is emitting red light at a wavelength of 700 nm and another light source is emitting ultraviolet light at a wavelength of 350 nm. Each photon of the ultraviolet light has | twice the energy of each photon of the red light. |
| In a beam of radiation, the amounts of energy per second at an ultraviolet wavelength of 300 nm and at an infrared wavelength of 800 nm are found to be equal. In this beam, how do the numbers of photons per second at each of these wavelengths compare? | There will be more IR photons than UV photons |
| In the photoelectric effect, electrons are ejected from the surface of a metal when light shines on it. What key characteristic of the photoelectric effect convinced Einstein that light is made up of photons? | Only light of a wavelength shorter than a certain value ejects electrons. Longer-wavelength light never ejects electrons, no matter how long it shines on the metal. |
| The coudé focus of a telescope is used at many observatories to | carry light to a remote, fixed focus where heavy and bulky equipment can be mounted. |
| A telescope has a 50cm focal length objective lens and a eyepiece of 2cm focal length. Another telescope has an objective lens with twice the focal length and an eyepiece of half the focal length. What magnifying power does one have compared to the other? | four times the magnifying power (two divided by one-half = four) |
| An amateur astronomer has a telescope with an objective lens of diameter 20 cm and focal length 100 cm. What focal length of eyepiece should he choose to obtain a magnification of 50X ("50 power")? | 2 cm |
| Many fortunate amateur astronomers have telescopes with primary mirrors 20 cm in diameter. The Keck telescopes on Hawaii have mirrors 10 m in diameter. How much more light is collected by one of the Keck telescopes compared to the amateur's telescope? | 2500 times more |
| The main reason electronic CCD cameras (and also photographic film) are superior to the human eye for studying astronomical objects through telescopes is that they are | able to store and integrate light for a long period, whereas the eye clears images several times a second. |
| Which of the following sentences correctly describes an advantage of a large refracting telescope over a large reflecting telescope? | A refracting telescope has no obstruction that blocks part of the light entering the telescope. |
| Spherical aberration in the primary mirror of a reflecting telescope is generally avoided by | making the mirror surface a parabolic shape. |
| The so-called seeing effect on the image of an astronomical source that causes "twinkling" of the image is produced by what effect in the Earth's atmosphere? | refraction of light by turbulent currents of air of differing density |
| The best available technique for achieving better angular resolution in large reflecting telescopes is to | rapidly change the shape of the telescope mirror. |
| What is involved in the astronomical technique of interferometry? | combination of signals from two or more widely spaced telescopes that are observing the same object |
| What is the primary reason astronomers combine the signals from several radio telescopes placed at widely separated locations around the Earth? | to attain much better angular resolution than is possible with a single telescope |
| What do the letters SOHO stand for? | Solar and Heliospheric Observatory |
| X-ray telescopes in space are primarily used for examining which kind of environment in the universe? | extremely hot regions around stars and galactic centers |
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