BRAINCAKERadio Telescopes
A radio telescope is a reflecting telescope for radio waves. A large parabolic dish reflects radio waves onto an antenna (the receiver) at its focus. The signal is amplified and processed by a computer to build up an image, one point at a time, as the dish is steered to scan the sky.
Similarities with optical reflecting telescopes: both use a parabolic reflector to bring waves to a focus, and both have collecting power proportional to D2 and resolution given by θ ≈ λ/D.
Differences:
• radio wavelengths (cm to m) are about a million times longer than visible light, so for the same diameter the resolving power is much poorer. Dishes must be very large (tens to hundreds of metres), and even then resolution is worse than a small optical telescope.
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Key terms in this lesson
- collecting power
- The amount of light energy collected by a telescope's objective lens or mirror per second, proportional to the square of its diameter.
- resolving power
- The ability of an optical instrument to distinguish between two objects that are close together, given by the minimum angular separation it can resolve.
More in Astrophysics
- Angular Magnification
- Reflecting Telescopes
- Chromatic and Spherical Aberration
- Resolving Power
- Charge-Coupled Devices
- Apparent Magnitude
- Parsecs and Light Years
- Absolute Magnitude
All 24 lessons in Astrophysics · All AQA A-level Physics topics