spectral windows through which electromagnetic radiation

1. Name the two spectral windows through which electromagnetic radiation easily reaches the surface of Earth (ie which part of the EM spectrum is opaque and transparent through the atmosphere).
2. List the largest-aperture single telescope currently in use in each of the following bands of the electromagnetic spectrum: radio, X-ray, gamma ray.
3. When astronomers discuss the apertures of their telescopes, they say bigger is better. Explain why.
4. The Hooker telescope at Palomar Observatory has a diameter of 5 m, and the Keck I telescope has a diameter of 10 m. How much more light can the Keck telescope collect than the Hooker telescope in the same amount of time?
5. What is meant by “reflecting” and “refracting” telescopes?
6. Why are the largest visible-light telescopes in the world made with mirrors rather than lenses?
7. Why is it difficult to observe at infrared wavelengths? What do astronomers do to address this difficulty?
8. Look at Figure 2 below which shows Cygnus A, and read its caption. The material in the giant lobes at the edges of the image had to have been ejected from the center at least how many years ago?

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