a) For a single dish radio telescope, such as the 76-m Lovell Telescope at Jodre
ID: 3161040 • Letter: A
Question
a) For a single dish radio telescope, such as the 76-m Lovell Telescope at Jodrell Bank Observatory operating at a frequency of 1.8 GHz, the smallest angular separation obtainable is hundreds of arc seconds, considerably greater than for an optical telescope such as the 8m Gemini. Explain why this is so (with example calculations).
b) Explain why ground-based optical telescopes do not achieve this theoretical resolution in practice.
c) Describe briefly how large telescopes, such as Gemini North, manage to overcome the limit described above, especially when working in the infrared spectral region.
Explanation / Answer
a) First of all, we should know how the radio telescope works. It uses a parabolic metal dish to reflect the radio waves in a signal detector or antenna whose position is above the dish. Then the signals go to the amplifier for magnification and then the signal is converted into images. Now those radio signals come from a large distance, therefore they often come on earth as the faint signals. So the radio telescopes are made large to detect and cover those signals. Again optical wavelengths are shorter than radio wavelengths and that means the radio waves are with very low energy so the large size of radio telescope identifies the low energy signals with clarity
b) In case of ground-based telescope, the photons (light particles) random direction changing movement disturb the image clarity and send blurring signals. So these telescopes do not achieve theoretical resolution.
c) Only 1% of light properly travels through earth's atmosphere, therefore large telescopes with large reflecting dish in highly elevated locations easily catch the lowe energy light particles.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.