OZ2 - Screening the Sun
Why is the atmosphere such a good sunscreen?
Most absorption occurs in the upper atmosphere - stratosphere.
Ozone is formed of oxygen (O3)
Absorbs in UV region 10.1 x 10(14) - 144.0 x 10(14).
Includes UV-B and UV-C
- causes damage to DNA
- skin cancer
- damage to eyes (cataract)
- damages crops
Ozone in the stratosphere protects us. Ozone in the troposphere is a significant pollutant.
Some atmospheric gases absorb UV strongly.
Ozone involved in chemical reactions producing photochemical smog
Causes haziness and reduced visibility and irritation and respiratory problems.
Higher up in the atmosphere the radiation is powerful enough to knock off electrons from atoms, molecules forming radicals.
Speed of light (ms-1) = wavelength (m) x frequency (s-1)
Energy of photon (J) = Plank's constant (Js) x frequency (s-1)
Molecules always have energy and move.
Translational energy
Rotational energy - absorbed from microwave.
Vibrational energy - energy absorb in the infrared range and this makes the bonds vibrate more, turning energy in the radiation into kinetic energy.
Electronic energy - (i.e. electrons jump to higher levels) higher energy than vibrational - corresponds to visible and ultraviolet.
