Light and Atmospheres

• Greenhouse gases absorb infrared light

• Scattering of visible wavelengths depends on wavelength

• Molecular dissociation by ultraviolet light

• Ionization by X-rays

Atmospheric Layers

Greenhouse Effect

Blue Sky: Scattered Light

UV and X-ray Light

• Ozone (O3) in stratosphere of Earth absorbs ultraviolet light.– Chemical balance between O3 and O2

– Chlorofluorocarbons (CFCs) destroy ozone

• X-rays ionize the upper layers of the atmosphere (ionosphere)– Charged particles reflect low frequency radio

waves (e.g., AM radio)

Atmospheric Windows

• Certain wavelengths require orbiting telescopes• Radio and visible light can be done from ground

Seeing: Atmospheric Effect

Why Put a Telescope in Orbit?

• The only reason to put a telescope in space is to eliminate atmosphere!

• a) ground-based b) damaged Hubblec) enhanced image d) repaired Hubble

Mauna Kea