Radio, UV, Infrared and X-ray telescopes

AQA A-level physics options - astrophysics chapter 1 telescopes.

Draw a diagram of a single-dish radio telescope.

• dish must be parabolic

• dish reflects signal to the antenna, the signal is amplified and then computer-analyzed.

Why must the dishes be large on single-dish radio telescopes?

• Radio telescopes collect EM radiation with very large wavelengths

• When wavelength is large, angular resolution is also large, resulting in large airy disks

• Therefore, the diameter of the dish must be large to reduce angular resolution.

• Large dish increases the resolving power and collecting power of the telescope

Advantages of radio telescopes

• Can operate during the day as well as night

• Many celestial objects active in the radio region (protostars, radio galaxies)

• De-excitation produces radio radiation. Hydrogen gas is everywhere in the universe, therefore radio telescopes are useful in detecting hydrogen clouds

Disadvantages of radio telescopes.

• Poor angular resolution compared to optical telescopes

• Ionosphere can absorb signals below 30MHz

• Water vapour absorbs singals above 60GHz

• Man-made interference at radio wavelengths (phones, radio, tv) forces telescopes to isolated areas.

• Require large structures for support and steering.