MAP TAP The Electromagnetic Spectrum5 Light Waves Properties of light waves include speed, frequency and wavelength Speed (s), frequency (f) and wavelength ( ) are related in the formula x f = s All EM waves travel at a speed of 300,000 km/s in a vacuum EM waves will travel at slower speeds through medium such as air, water and glass
MAP TAP The Electromagnetic Spectrum6 Wavelength, Frequency and Energy Light with a short wavelength will have a high frequency and high energy. Light with long wavelengths have low frequencies and low energy
MAP TAP The Electromagnetic Spectrum7 Chapter 22 Section 2 The Electromagnetic Spectrum
MAP TAP The Electromagnetic Spectrum8
MAP TAP The Electromagnetic Spectrum9 Electromagnetic Spectrum The electromagnetic spectrum is the complete spectrum or continuum of light including radio waves, infrared, visible light, ultraviolet light, X- rays and gamma rays
MAP TAP The Electromagnetic Spectrum10
MAP TAP The Electromagnetic Spectrum11 Radio waves Low energy waves with long wavelengths and low frequencies Includes FM, AM, radar and TV waves Used in many devices such as remote control items, cell phones, wireless devices, etc. AM has longer wavelength, is used for audio portion of TV broadcasts and its long wavelength can bend around hills.
MAP TAP The Electromagnetic Spectrum12 Modulating Radio Waves Modulation – variation of amplitude or frequency when waves are broadcast AM – amplitude modulation FM - frequency modulation
MAP TAP The Electromagnetic Spectrum13 AM and FM AM – carries audio for TV broadcasts and its longer wavelengths bend around hills and tall buildings FM – carries video for TV broadcasts
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MAP TAP The Electromagnetic Spectrum15 Microwaves First used in radar, now used in communication, medicine and consumer use (microwave ovens)
MAP TAP The Electromagnetic Spectrum16 Infrared waves Invisible electromagnetic waves that are detected as heat Can be detected with special devices such as night goggles Used in heat lamps
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MAP TAP The Electromagnetic Spectrum18 Visible Light The portion of the electromagnetic spectrum that human eyes can detect ROY G BIV (red, orange, yellow, green, blue, indigo, violet) Red is the lowest frequency and violet is the highest frequency
MAP TAP The Electromagnetic Spectrum19
MAP TAP The Electromagnetic Spectrum20 Ultraviolet waves Higher energy than light waves Can cause skin cancer and blindness in humans Used in tanning beds, food processing and sterilizing equipment in hospitals, food processing Helps your body absorb Vitamin D
MAP TAP The Electromagnetic Spectrum21 X-Rays High energy waves First discovered by Roentgen Used in medicine, industry and astronomy Can cause cancer Bones absorb x-rays but soft tissue does not Lead absorbs X-rays
MAP TAP The Electromagnetic Spectrum22 Gamma rays Highest energy Shortest wavelength Come from outer space Blocked from Earth’s surface by atmosphere Can be used in cancer treatments
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MAP TAP The Electromagnetic Spectrum24 Time to think….. 1. What is the relationship between frequency and wavelength? 2. What is meant by ‘spectrum’? 3. What does ROY G BIV mean?
MAP TAP The Electromagnetic Spectrum25 Now, let’s really think 4. Can you actually see x-rays? –Support your answer. 5. Which color is more energetic, red or yellow? 6. Which type of wave travels faster, gamma or radio? 7. Why are microwaves more dangerous than radio waves?
MAP TAP The Electromagnetic Spectrum26 Think about it…. You have just been involved in a traffic incident that leaves you stranded on the side of the road. Which part of the electromagnetic spectrum would be of the most use to you and why?
MAP TAP The Electromagnetic Spectrum27 Answers 1. Frequency and wavelength are properties of waves and since speed is constant for EM waves, as frequency increases, wavelength decreases. 2. Spectrum is a continuum of all electromagnetic waves 3, ROY G BIV is the difference colors of the visible light in order of longest wavelength to shortest wavelength. 4. X-rays can not be seen, only the waves in the visible light portion are visible. 5. Yellow is higher energy than red because it has a shorter wavelength and higher frequency. 6. Both travel at the same speed, 300,000 km/s (all em waves travel at the same speed) 7. Microwaves have a higher frequency than radio and carry more energy.
MAP TAP The Electromagnetic Spectrum28 Chapter 22 Section 3 Interactions of Light
MAP TAP The Electromagnetic Spectrum29 Refraction of Light Refraction – Bending of light due to a change in speed. –Index of Refraction – Amount by which a material refracts light. –Prisms – Glass that bends light. Different frequencies are bent different amounts & light is broken out into different colors.
MAP TAP The Electromagnetic Spectrum30 Refraction – bending of light
MAP TAP The Electromagnetic Spectrum31 Diffraction & Refraction Diffraction – Bending of waves around the edge of a barrier. New waves are formed from the original. breaks images into bands of light & dark and colors. Refraction – Bending of waves due to a change in speed through an object.
MAP TAP The Electromagnetic Spectrum33 Reflection Reflection – Bouncing back of light waves –Regular reflection – mirrors smooth surfaces scatter light very little. Images are clear & exact. –Diffuse reflection – reflected light is scattered due to an irregular surface.
MAP TAP The Electromagnetic Spectrum34 Chapter 22 Section 4 Light and Color
MAP TAP The Electromagnetic Spectrum43 L Real Image – –Image is made from “real” light rays that converge at a real focal point so the image is REAL –Can be projected onto a screen because light actually passes through the point where the image appears –Always inverted
MAP TAP The Electromagnetic Spectrum44 Virtual Image– –“Not Real” because it cannot be projected –Image only seems to be there!
MAP TAP The Electromagnetic Spectrum48 Lenses Convex Lenses –Thicker in the center than edges. –Lens that converges (brings together) light rays. –Forms real images and virtual images depending on position of the object
MAP TAP The Electromagnetic Spectrum62 Telescopes Refracting telescopes – use two convex lenses Reflecting telescopes use a concave mirror to bounce the light to a plane mirror which reflects the light to a convex lenses
MAP TAP The Electromagnetic Spectrum63 LIGHT & USES: Optical Instruments LASERS –Acronym: Light Amplification by Stimulated Emission of Radiation –Coherent Light – Waves are in phase so it is VERY powerful & VERY intense.
MAP TAP The Electromagnetic Spectrum64 LIGHT & USES: Optical Instruments LASERS –Holography – Use of Lasers to create 3-D images –Fiber Optics – Light energy transferred through long, flexible fibers of glass/plastic –Uses – Communications, medicine, t.v. transmission, data processing.
MAP TAP The Electromagnetic Spectrum65 Polarized Light Light waves vibrate in only one plane or direction. Can cause glare. Be sure your sunglasses are polarized to reduce the glare.
MAP TAP The Electromagnetic Spectrum66 Communication Technology Cordless phone – phone & radio signals Cellular phone – mainly uses microwaves to send signals Satellite TV – uses microwaves Global Positioning System (GPS) – uses microwaves and satellite system (24) – need a signal from at least 4 satellites to find a location.