2. What Is Sunlight? Sunlight is the total spectrum of the electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the atmosphere, and the solar radiation is obvious as daylight when the Sun is above the horizon. Near the poles in summer, the days are longer and the nights are shorter or non-existent. In the winter at the poles the nights are longer and for some periods of time, sunlight may not occur at all. When the direct radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and heat.spectrum electromagnetic radiationSunEarthfiltered atmosphere daylighthorizonpoles

3. Importance of Sunlight to Humans

4. Importance of Sunlight to Environment

5. Importance of Sunlight to Humans and Environment A healing agent Increases the number of white blood cells - the body's primary defense against body infections. Sunlight has also been shown to improve your mood and regulate your sleep patterns. If you have sore, aching muscles then sunlight can improve the circulation to your skin and ease some of your discomfort. Sunlight provides Vitamin D (Maintains Your Calcium Balance) Through the energy from the sunlight, the plants perform photosynthesis to convert carbon dioxide into organic compounds, especially sugars.

6. If there’s no Sunlight… There’s actually NO LIFE! Sunlight is necessary for plants to grow, and to provide energy to warm the earth's atmosphere.

7. Sunlight Includes: Infrared Light-The name means below red (from the Latin infra, "below"), red being the color of the longest wavelengths of visible light. IR light has a longer wavelength than that of red light. Visible Light-is the portion of the electromagnetic spectrum that is visible to (can be detected by) the human eye. electromagnetic spectrumvisibleeye Ultraviolet Light-light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than x-rays.electromagnetic radiationwavelength visible lightx-rays

8. Ultraviolet Rays It is so named because the spectrum consists of electromagnetic waves with frequencies higher than those that humans identify as the color violet.humans violet

9. Effects of Ultraviolet Light

10. Beneficial Effects of UV Light Vitamin D -The Earth's atmosphere blocks UV radiation from penetrating through the atmosphere by 98.7%. A positive effect of UVB exposure is that it induces the production of vitamin D in the skin.vitamin D Aesthetics -Too little UVB radiation leads to a lack of Vitamin D. Too much UVB radiation leads to direct DNA damages and sunburn. An appropriate amount of UVB (which varies according to skin color) leads to a limited amount of direct DNA damage. This is recognized and repaired by the body. Then the melanin production is increased which leads to a long lasting tan.direct DNA damagesskin color Medical applications -Ultraviolet radiation has other medical applications, in the treatment of skin conditions.

11. Harmful Effects of UV Light Skin - An overexposure to UVB radiation can cause sunburn and some forms of skin cancer. sunburn Eye -High intensities of UVB light are hazardous to the eyes, and may lead to some eye damages such as cataracts. If too much UV light is absorbed, eye structures such as the cornea, the lens and the retina can be damaged. cornealensretina

13. What is Ozone Layer? The ozone layer is a layer in Earth's atmosphere which contains relatively high concentrations of ozone (O3). This layer absorbs 93-99% of the sun's high frequency ultraviolet light, which is potentially damaging to life on earth.Earth's atmosphereozonesunultraviolet light

14. Importance of Ozone OzoneOzone is a gas that occurs naturally in relatively large concentrations in the upper-atmospheric layer known as the stratosphere. Stratospheric ozone is very important to life on the surface of Earth because it absorbs much of the incoming solar ultraviolet radiation, and thereby shields organisms from its deleterious effects.Earthradiation It filters UV Light.

15. Ozone Depletion Ozone depletion describes two distinct, but related observations: a slow, steady decline of about 4% per decade in the total volume of ozone in Earth's stratosphere (ozone layer) since the late 1970s, and a much larger, but seasonal, decrease in stratospheric ozone over Earth's polar regions during the same period.ozoneEarth'sstratosphere

16. Causes of Ozone Depletion The production and emission of CFCs, chlorofluorocarbons, is by far the leading cause. -CFCs came to be used in refrigerators, home insulation, plastic foam, and throwaway food containers. -Only later did people realize the disaster CFCs caused in the stratosphere. There, the chlorine atom is removed from the CFC and attracts one of the three oxygen atoms in the ozone molecule. The process continues, and a single chlorine atom can destroy over 100,000 molecules of ozone.

17. Effects of Ozone Depletion

18. More ultraviolet light from the sun can reach the Earth. The increased cancer levels caused by exposure to this ultraviolet light could be enormous. It may lead to Global Warming. The EPA estimates that 60 million Americans born by the year 2075 will get skin cancer because of ozone depletion. Some research shows that a decreased ozone layer will increase rates of malaria and other infectious diseases.

19. Continuation… The environment will also be negatively affected by ozone depletion. The life cycles of plants will change, disrupting the food chain. Oceans will be hit hard as well. The most basic microscopic organisms such as plankton may not be able to survive. If that happened, it would mean that all of the other animals that are above plankton in the food chain would also die out. Other ecosystems such as forests and deserts will also be harmed. Wind patterns could change, resulting in climatic changes throughout the world.

20. Ways to protect Ozone Layer Try to use products which are labeled "Ozone- Friendly" Ensure technicians repairing your refrigerator or air conditioner recover and recycle the old CFCs so they are not released into the atmosphere. Vehicle air conditioning units should regularly be checked for leaks. Ask about converting your car to a substitute refrigerant if the a/c system needs major repair Help start a refrigerant recovery and recycling program in your area if none already exists.

21. Continuation… Replace halon fire extinguishers with alternatives (e.g. carbon dioxide or foam). Suggest school activities to increase awareness of the problem and to initiate local action.

22. Ozone Layer if CFCs hadn’t been banned