Test 2 Astronomy

The person who first showed that light is an electromagnetic wave was

• James Clerk Maxwell in the 1860s

• Albert Einstein in 1905

• Thomas Young in 1801

The first person to prove that light did not travel at infinite speed was

• Ole Romer

• Albert Einstein

• Galileo Galilei

A flash of light is transmitted simultaneously through two parallel tubes of length 1 km, one evacuated, the other filled with water. Detectors sense the arrival times of the light flash at the ends of these tubes. What will be the relationship between arrival times of these light flashes?

• The flash will arrive earliest through the water filled tube.

• The flashes will arrive simultaneously at the ends of the tubes because light always travels at the same speed.

• The flash will arrive earliest through the evacuated tube.

The frequency associated with blue light compared to the frequency of red light is

• The same because both red and blue are part of the visible light spectrum.

• higher.

• lower.

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

• half the energy of each photon of the red light

• either more or less energy than each photon of the red light, depending on the intensities of the two light sources

• twice the energy of each photon of the red light

In a particular 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 number of photons per second at each of these wavelengths compare?

• There will be equal numbers of photons at each of these wavelengths

• There will be more IR photons than UV photons

• There will be more UV photons than IR 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 not matter how long it shines on the metal

• Electrons are ejected in sequences of short burst rather than continuously, showing that the light energy arrives as bundles of energy

• Electrons are ejected rapidly by short wavelength light and only slowly by long wavelength light

The coude 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

• focus light at a convenient point just behind a hole in the primary mirror

• lace the focus close to and on the side of the telescope, near a small, flat, diagonal mirror

An amateur astronomer is using a telescope that has a 50 cm focal length objective lens and an eyepiece of 2 cm focal length. His sister is using a telescope with an objective lens having twice the focal length and an eyepiece of half the focal length. What overall magnifying power does his sister's telescope have compared to his own?

• the same magnifying power (two times one half=one)

• four times the magnifying power (two divided by one half=four)

• twice the magnifying power (because of the longer focal length objective lens)

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)?

• .4 cm

• 2 cm

• .5 cm