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14.2 – NOTES Solar Radiation

14.2 – NOTES Solar Radiation. The Earth’s atmosphere is needed for several reasons Midday sun would fry eggs on rock UV rays would burn skin Nights would be cold enough to freeze CO 2 into a solid, in the form of dry ice Sun’s radiant energy and atmospheric gases make an hospitable climate

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14.2 – NOTES Solar Radiation

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  1. 14.2 – NOTESSolar Radiation

  2. The Earth’s atmosphere is needed for several reasons • Midday sun would fry eggs on rock • UV rays would burn skin • Nights would be cold enough to freeze CO2into a solid, in the form of dry ice • Sun’s radiant energy and atmospheric gases make an hospitable climate • The atmosphere acts as a reservoir/storage unit for oxygen and carbon dioxide • It also protects us from harmful radiation and moderates temperature

  3. B.1 The Electromagnetic Spectrum and Solar Radiation • Sun’s energy is a result of nuclear fusion • Fusion is combining 2 small nuclei into 1 larger nucleus • The reaction is extremely exothermic (releases a lot of energy)

  4. Electromagnetic radiation • Energy liberated through fusion in the sun is transmitted to earth as electromagnetic radiation • Electromagnetic spectrum • Shows wavelengths and frequencies of various wave types, but all waves have the same speed • Type of ER represents a particular wavelength and frequency • Radio, micro, infrared, visible light, UV, x-rays, gamma rays, cosmic rays

  5. Made of photons • Small packets of light that travel as waves • Photons transfer energy as they collide/interact with matter

  6. Electromagnetic radiation travels as wave • Do not require a medium to travel through- can move through a vacuum as well as air • They oscillate, therefore have • Frequency- f – the number of waves that pass a given point per second, unit is Hertz (Hz) • Hertz– 1/s or s-1 • Wavelength- l - distance between the top of two successive waves • C= l * f • C = speedoflight = 3 x 108 m/s – all electromagnetic radiation moves at this speed • l = wavelength (m) • F = frequency (1/s)

  7. Solar radiation • The radiant energy given off by the sun is spread over a large portion of the spectrum • The majority of the radiation falls in three regions 45% in IR region 46% in visibleregion 9% in UV region

  8. Infrared radiation (IR) • Frequencies slightly lower than visible red light, and wavelength is slightly longer • Causes certain bonded atoms to vibrate more energetically, which increase the object’s temperature • Most is absorbed by CO2 and H2O in the atmosphere • This was demonstrated by Tyndall in 1860s • This process reradiates energy back into the atmosphere, where it is retained and helps to warm the atmosphere

  9. Visible radiation • More than 90% reaches the surface on a clear day • Can energize electrons in some bonds • Interacts with electrons is chlorophyll molecules, which provides the energy needed for photosynthesis

  10. Ultraviolet radiation • The most harmful radiation given off by the sun • Three separate categories • UV-A • Longest wavelength, lowest energy Longer than 320 nm Most absorbed by ozone layer Effects: tanning, sunburn, DNA damage, skin cancer

  11. UV-B • 280-320 nm • Most absorbed by stratospheric ozone layer • Effects: sunburns, skin cancer, DNA damage

  12. UV-C Most energetic of the three UV types Blocked by the ozone layer Wavelengths shorter than 280 nm Have enough energy to break covalent bonds Used to sterilize materials because it can kill bacteria and destroy viruses Effects: DNA and tissue damage, kills bacteria and viruses

  13. Humans need some UV radiation to produce vitamin D

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