Electromagnetic Spectrum • Energy from the Sun travels as electromagnetic waves or EM waves. • They are waves that transfers energy though a field. • Do not require matter to transfer its energy— occurs in a vacuum. Ocean waves need water Sound waves need air. Parts of a Wave 1. Crest- High point of wave. 2. Trough- Low point of wave. Electromagnetic Waves Described by their physical wave features 3. Amplitude- Height of wave from center line to crest or trough. 4. Wavelength- Distance b/w 2 crests or troughs. 5. Frequency- # of waves passing a point each second. Diagram of a Wave Arrangement • Arranged according to their increasing frequency and decreasing wavelength. • All electromagnetic waves travel at the same speed. • Amt of energy carried by an electromagnetic wave increases with frequency. Electromagnetic Spectrum • Each wavelength of EM energy interacts with objects on Earth in a different way. • Some are reflected and some are absorbed. • Color results from a combination of both interactions. • When light strikes a leaf, leaf absorbs red light and but reflects green light. • Reflected green light enters your eye—so you see a green leaf. • Each type of matter has its own signature, called a reflectance curve, that shows how it reflects and absorbs energy. • A reflectance curve is a graph that shows how a type of matter reflects visible, infrared and other wavelengths of light. • Upward curve on graph indicates more of the wavelength is reflected. • Downward curve on graph shows more of the wavelength is absorbed. Radio Waves • Lowest frequencies and longest wavelengths. • TV broadcast- Sound portion carried by AM waves (amplitude modulation) while picture portion carried as FM waves (frequency modulation). • MRI- magnetic resonance imaging. Does not harm cells. • Radio telescopes • Microwaves-highest frequency rw. Food Most common use is cell phones. • Radar Infrared Rays • Cannot be seen • Can be felt as heat- light bulbs, stove, sun. • Warmer object= more infrared rays • Cool object= absorb energy from infrared waves and become hotter. • Infrared lamps keep food hot, relieve sore muscles, and dry paint and hair. • Infrared camaras • Thermograms • Study pieces of art Visible Spectrum • The only electromagnetic waves you can see. • ROY G BIV red, orange, yellow, green, blue, indigo and violet. • Half of energy given off by sun is visible light. • Essential for photosynthesis. Ultraviolet Rays • Electromagnetic waves with frequencies just higher than visible light. • Energy of UV rays can kill cells. • Used to kill germs in hospitals • Preserve food in processing plants. • Can be seen by many insects. • UV rays cause your skin cells to produce Vitamin D • Tanning is body’s way of protecting itself from UV rays. Can cause damage to skin, eyes and immune system X-Rays • Energy of X-rays allows it to pass through materials. • Used to take pictures of bone because bone absorbs X-rays. • Exposure of X-rays over a long period of time can cause defects in cells. • Been detected deep in space-believed to be in exploding stars. Gamma Rays • Highest frequencies and shortest wavelengths. • Have highest energy in spectrum. • Radioactive materials and nuclear reactions emit gamma rays. • Can penetrate 3-m of concrete. • Gamma camara-patient is injected with a fluid that emits gamma rays. Move the camara over the body to form an image.
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