Astronomy Module 5
In this Interactive, there are two animated light waves on the screen. Between them is a labeled wavelength axis. Is Infrared light at a wavelength of 1×10^-5 meters "visible" or "invisible"?
invisible
The speed of a light wave:
is independent of its other properties
An electromagnetic wave is
light
Among the following, which is the most important reason to make telescopes large?
light-collecting power
In this Interactive, there are two animated light waves on the screen. When the Interactive starts, the bottom wave is set up with the same wavelength (and thus frequency) as the top wave. However, the slider in the lower left allows you to adjust the wavelength (λλ) of this bottom light wave. The wavelength (λλ) and frequency (f) of a light wave are related to each other and the speed of light (c) by the expression f=c/λ.Given the speed of light is a constant c = 2.998×10^8 m/s, compute the frequency of light with a wavelength of λ = 0.00 meters.
0s^-1
Which of the following are not found in the electromagnetic spectrum?
Cosmic rays Sound waves
For each of the five possible astronomical targets, place them on the figure of wavelength versus atmospheric opacity based on the wavelength you would most easily observe them at.
From left to right: Gamma ray burst Black hole accretion disk Sun Planets, star-forming clouds Radio Galaxy
In this Interactive, there are two animated light waves on the screen. The top wave is a constant wave of light with a red color corresponding to a wavelength of about 685 nm (6.85×10^−7 m). Notice that every time a peak in the wave passes the right-hand side of the window, a red sphere above the right-hand side of the wave flashes. The number of wave peaks per second passing a point is called the frequency. When the Interactive starts, the bottom wave is set up with the same wavelength (and thus frequency) as the top wave. However, the slider in the lower left allows you to adjust the wavelength (λ) of this bottom light wave. Notice that the frequency with which the sphere above the right-hand side of the wave flashes also changes as the wavelength changes for the bottom wave. NOTE: You may also notice a small "eye" icon next to the flashing sphere. When the eye icon has a red hash through it, the light at this wavelength is not visible to the human eye. Rank the following kinds of light by frequency from highest (top) to lowest (bottom).
Highest Ultraviolet Blue visible light (left-most visible light on axis) Green visible light (middle of visible range) Red visible light (right-most visible light on axis) Infrared Lowest
Following the invention of the telescope, astronomers were able to measure the speed of light by observing Jupiter's moons passing behind Jupiter in their orbit and becoming eclipsed. Study the figure, which shows how someone on Earth can view Jupiter's moon's eclipses when Earth is closer to or farther from Jupiter, and determine which of the following are correct.
If light has finite speed, it would take longer for it to travel from Jupiter to Earth when Earth is farther from Jupiter. If light has infinite speed, an eclipse would be seen to happen at the same time regardless of how far away Earth is from Jupiter.
A typical amateur telescope is a 10-inch reflector (where "10-inch" refers to the diameter of the telescope's mirror). How does the light-gathering power of the Hooker 100-inch reflector on Mount Wilson compare with that of the amateur telescope?
It is 100x greater.
In this Interactive, there are two animated light waves on the screen. The top wave is a constant wave of light with a red color corresponding to a wavelength of about 685 nm (6.85×10^−7 m). When the Interactive starts, the bottom wave is set up with the same wavelength. However, the slider in the lower left of the Interactive allows you to adjust the wavelength (λ) of this bottom light wave. As you move the slider, notice that the blue vertical indicator on the wavelength axis between the two waves moves to indicate the wavelength. Experiment with it, sliding it to the right (or left) to increase (or decrease) the wavelength. Rank the following kinds of light by wavelength from longest wavelength (top) to shortest wavelength (bottom).
Longest Infrared Red visible light (right-most visible light on axis) Green visible light (middle of visible range) Blue visible light (left-most visible light on axis) Ultraviolet Shortest
Changing the wavelength of visible light changes its color. If the wavelength is decreased or increased outside of the range of wavelengths our eyes can detect, the light becomes invisible to us, but it is still fundamentally light. Examine the figure, which shows the entire electromagnetic spectrum and includes all types of light as a function of wavelength. Given what you learned from the figure, rank these types of light in order of increasing energy.
Lower Energy Radio Infrared Orange Green Ultraviolet Gamma Ray Higher Energy
Which of the following is NOT an advantage of a reflecting telescope over a refracting telescope?
Mirrors provide stronger magnification than lenses
Arrange the following regions of the electromagnetic spectrum from lowest to highest frequency.
Radio Infrared Optical Ultraviolet X-ray Gamma Ray
Why do stars twinkle?
The motion of Earth's atmosphere creates the appearance of twinkling.
Space telescopes that exist in orbit above most of Earth's atmosphere are expensive, so they must therefore be supported with a very compelling motivation. If you were trying to justify funding for a space telescope in orbit around the Earth, which of the following would be the best argument to use?
The telescope could observe wavelengths of light that are not visible from the ground.
Two light waves have wavelengths of 200 nm and 400 nm, respectively. How are their frequencies related?
The wave with a 200 nm wavelength has twice the frequency of the 400 nm wave.
In this interactive, there are two animated light waves on the screen. The top wave is a constant wave of light with a red color corresponding to a wavelength of about 685 nm (6.85 × 10-7 m). Notice that every time a peak in the wave passes the right-hand side of the window, a red sphere above the right-hand side of the wave flashes. The number of wave peaks per second passing a point is called the frequency. When the interactive starts, the bottom wave is set up with the same wavelength (and thus frequency) as the top wave. However, the slider in the lower left allows you to adjust the wavelength (λ) of this bottom light wave. Explore what happens when you adjust the slider and then sort the following short statements into "true" or "false" statements about light.
True: Infrared has higher wavelength than red. If frequency goes up, wavelength drops. If wavelength goes up, frequency drops. False: Infrared has higher frequency than red. If frequency goes up, so does wavelength. As wavelength drops, so does frequency.
Which of the following properties of a telescope determines whether two closely spaced objects spaced objects can be seen in an astronomical image?
angular resolution
Stars twinkle because of:
atmospheric turbulence
Which of the following varieties of light has the LOWEST frequency?
blue
Light is
both a particle and a wave
Place the following varieties of light in order, from lowest to highest frequency: infrared, ultraviolet, microwave, visible, gamma rays
microwave, infrared, visible, ultraviolet, gamma rays
When you turn on a lightbulb in a room, the entire room appears to flood with light at the same time. Your eyes cannot perceive light originating at the bulb and then moving outward from it. This either means that light has infinite speed (appears everywhere instantaneously), or it moves so fast that it is difficult to tell the difference. How might you improve your chances of detecting the motion of light if it moves at finite speed?
move farther away from the light source
Which of the following types of light has the highest atmospheric transmission?
radio
ROYGBIV is?
the correct order for the colors of the rainbow
Which of the following portions of the electromagnetic spectrum must be observed from space?
ultraviolet
Which of the following varieties of light has the SHORTEST wavelength?
ultraviolet
The atmosphere absorbs some light before it can reach a telescope's detector, making objects appear fainter. The exact amount of absorption depends on the wavelength of light being observed, as shown in this graph of the percentage of light that can make it through the atmosphere to the ground. 0% transparency (atmosphere is opaque) means no light gets through, and 100% transparency means all the light gets through. The type of light per wavelength is labeled at the bottom of the figure. Visible light is marked by the rainbow. Based on the above graph, which of these types of light from astronomical sources are not observable from the ground?
ultraviolet at 100 nm x-ray infrared at 100 micrometer (10^-4 m) gamma ray
