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Chapter 6: Problem 25

What are the optical window and the radio window? Why isn't there an X-ray window or an ultraviolet window?

Short Answer

Expert verified
The optical window and radio window refer to the parts of the electromagnetic spectrum that can be observed from Earth. The absence of X-ray and ultraviolet windows is due to the atmospheric absorption of such waves, blocking them from reaching the Earth's surface.

Step by step solution

01

Define the Optical Window

The 'optical window' refers to the wavelengths of the electromagnetic spectrum that can be observed by optical telescopes from the Earth's surface. These wavelengths are roughly between 300 and 1100 nm, which cover ultraviolet, visible and near-infrared light.
02

Define the Radio Window

The 'radio window' refers to the range of frequencies of the electromagnetic spectrum allowed to pass through the Earth's atmosphere, in which astronomical observations can be made by radio telescopes. This window spans from about 1 GHz (30 cm wavelength) to 1 MHz (300 m wavelength).
03

Explanation for the absence of X-ray and Ultraviolet Windows

The Earth's atmosphere absorbs X-rays and most of the ultraviolet light before reaching the ground, making observations in these parts of the spectrum impossible from the Earth's surface. Therefore, there are no 'X-ray window' or 'ultraviolet window' because these wavelengths cannot pass through the Earth's atmosphere.

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Most popular questions from this chapter

Suppose your Newtonian reflector has an objective mirror \(20 \mathrm{~cm}\) ( 8 in.) in diameter with a focal length of \(2 \mathrm{~m}\). What magnification do you get with eyepieces whose focal lengths are (a) \(9 \mathrm{~mm}\), (b) \(20 \mathrm{~mm}\), and (c) \(55 \mathrm{~mm}\) ? (d) What is the telescope's diffraction-limited angular resolution when used with orange light of wavelength \(600 \mathrm{~nm}\) ? (e) Would it be possible to achieve this angular resolution if you took the telescope to the summit of Mauna Kea? Why or why not?

Use the Stary Night Enthusiast \({ }^{\mathrm{TM}}\) program to explore the concept of angular resolution. Click the Find tab to the left of the main view window to open the Find pane. Click on the magnifying glass icon at the left- hand side of the edit box at the top of the Find pane and select the Orbiting Objects item from the dropdown menu that appears. This will bring up a list of Solar System objects in the Find pane. Double-click the entry labeled The Moon. You can zoom in and zoom out using the Zoom buttons at the right side of the toolbar. You can also rotate the Moon by putting the mouse cursor over the image, holding down the mouse button and the Shift key on the keyboard, and moving the mouse. (On a two-button mouse, hold down the left mouse button.) (a) What is the size of the smallest detail that you can see? (You will have to make measurements on the screen using a ruler and compare it to the diameter of the Moon, which is \(3476 \mathrm{~km}\).) (b) The angular resolution of the Hubble Space Telescope (HST) is \(0.1\) arcsec. How far away from the Moon could HST be and still be able to resolve details as small as you determined in part (a)? Give your answer in kilometers and in astronomical units (AU).

Explain why the light rays that enter a telescope from an astronomical object are essentially parallel.

No major observatory has a Newtonian reflector as its primary instrument, whereas Newtonian reflectors are extremely popular among amateur astronomers. Explain why this is so.

The Institute of Space and Astronautical Science in Japan proposes to place a radio telescope into an even higher orbit than the HALCA telescope. Using this telescope in concert with ground-based radio-telescopes, baselines as long as \(25,000 \mathrm{~km}\) may be obtainable. Astronomers want to use this combination to study radio emission at a frequency of \(43 \mathrm{GHz}\) from the molecule silicon monoxide, which is found in the interstellar clouds from which stars form. \((1 \mathrm{GHz}=\) 1 gigahertz \(=10^{9} \mathrm{~Hz}\).) (a) What is the wavelength of this emission? (b) Taking the baseline to be the effective diameter of this radio-telescope array, what angular resolution can be achieved?
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