There are two optical telescopes operating at the exact same frequency. The firs
ID: 2058910 • Letter: T
Question
There are two optical telescopes operating at the exact same frequency.The first telescope is a 10 m telescope that is planned to be located at the L2 Lagrangian point 1.5 million kilometers past the orbit of the Earth. The second telescope is a 2 m telescope that is planned to be placed on the far side of the moon (average distance to the moon is 380,000 km from the Earth..
A. Which telescope will have the greater light gathering power (10 m or 2 m)?
B. Explain your answer to part (A).
If the 10m telescope were placed on the Earth on top of Mauna Kea in Hawaii at 14000 feet instead of at L2, which telescope NOW has the greater light gathering power, by what factor
C.. The 10 m telescope has a _____ (greater/smaller. light gathering power
D.. by a factor of _____ times.
E. Compare your answers to parts C. and D. to your answer to part A.. Explain any differences.
Explanation / Answer
A. the 10m one B. both telescopes are in vacuum. The 10m one has area Pi r ^2, with r = 5m. The 2m one has r = 1. The ratio of Pi 5^2/Pi 1^2 = 25. Twenty-five times more light falls onto the large telescope. C. Greater. Normally, light gathering power ratios are just the ratios of the areas. On earth there could be some absorption due to the atmosphere, but they don't specify the wavelength, so that isn't correct. There would be a very small increase in the amount of light that hits the earth telescope since the atmosphere acts like a gradient index lens, refracting light towards the telescope (that would have continued at a larger angle and missed the telescope had there been no atmosphere) D. the effect of the air would be small, so it is has about 25 times the light gaterhing power.