IPC Waves, Sound, Light and Optics

1. IPC Waves, Sound, Light and Optics C. Smith

2. Waves, Sound, Light and Optics • 1. Define WAVE - a moving disturbance that transfers energy from one place to another2. List and define the two types of waves. TRANSVERSE WAVE - particles of the medium vibrate perpendicular to the direction the wave is moving. LONGITUDINAL WAVE (COMPRESSIONAL WAVE) - particles of the medium vibrate parallel to the direction the wave is moving

3. Waves, Sound, Light and Optics • 3.Identify these terms as they apply to a transverse wave: nodal line, crest, trough, amplitude and wavelength. • NODAL LINE - the usual resting position of the wave • CREST - uppermost point of a transverse wave • TROUGH - lowest point of a transverse wave • AMPLITUDE - the distance from the nodal line to the crest or nodal line to the trough • WAVELENGTH - the distance between two identical successive points on a wave (crest to crest or trough to trough)

4. Waves, Sound, Light and Optics • 4. Identify these terms as they apply to a longitudinal wave: compression, rarefaction and wavelength. • COMPRESSION - area where the molecules are packed closely together • RAREFACTION - area where the molecules are spread far apart • WAVELENGTH - the distance between any two identical successive points on a wave (compression to compression, rarefaction to rarefaction)

5. Waves, Sound, Light and Optics • 5. Define frequency and Hertz. • FREQUENCY - the number of waves that pass a given point in one second • HERTZ - the unit for frequency; waves per second • 450 waves per second = 450 Hz

6. Waves, Sound, Light and Optics • 6. Use the wave equation to solve for velocity, frequency or wavelength when two of the variables are known. • VELOCITY = FREQUENCY X WAVELENGTH • v =  • Velocity .......... meters per second (m/s) • Frequency ƒ .... waves per second (Hz) • Wavelength λ....... meters per wave (m)

7. Waves, Sound, Light and Optics • 7. List the three conditions necessary to have sound. • In order to satisfy the scientific definition of sound, there must be a source, medium and receiver. • SOURCE - something to vibrate and produce the sound wave • MEDIUM - something for the sound wave to travel through • RECEIVER - something to detect (hear) the sound wave

8. Waves, Sound, Light and Optics • 8. Relate the speed of sound to: • (a) density of the medium • (b) temperature of the medium • The more dense the medium, the faster sound travels. (solid, liquid, gas) • The higher the temperature within a medium, the faster sound travels. (hot air, cold air)

9. Waves, Sound, Light and Optics • 9. State the speed of sound in English and metric units. • The speed of sound can be expressed as: • 334 meters per second (m/s) • 1090 feet per second (ft/s) • 750 miles per hour (Mach 1)

10. Waves, Sound, Light and Optics • 10. Define echo and state the conditions necessary for a human to hear an echo. • ECHO - reflected sound wave • To hear an echo, the original sound and the returning sound must be at least 1/10 of a second apart. • Usually, this means the reflecting surface must be at least 55 feet away for a human to hear the echo.

11. Waves, Sound, Light and Optics • 11. Explain how echoes are prevented in auditoriums. • An echo is prevented by use of sound absorbing materials such as padded seats, curtains on the walls and carpeting.

12. Waves, Sound, Light and Optics • 12. Solve mathematical word problems involving ECHOES. • Use the formula v=d/t. If given the distance in an echo problem, this distance must be doubled in order to solve for time. If given the time in an echo problem, this time must be cut in half to solve for distance. • source >>>>>>>>> reflecting wall

13. Waves, Sound, Light and Optics Source Reflecting Wall

14. Waves, Sound, Light and Optics • 13. Distinguish between noise and musical tones. • NOISE - a series of irregular vibrations if shown on the screen of an oscilloscope • MUSIC - a series of regular or smooth patterns if shown on the screen of an oscilloscope

15. Waves, Sound, Light and Optics • 14. List the four types of musical instruments. • The four types of musical instruments are wind, string, percussion and electronic. • STRING INSTRUMENTS produce sounds by vibrating strings • WIND INSTRUMENTS produce sounds by a vibrating column of air • PERCUSSION INSTRUMENTS produce sound by a vibrating membrane • ELECTRONIC INSTRUMENTS produce sound by use of electricity and computers

16. Waves, Sound, Light and Optics • 15. Discuss ways to vary the frequency of a vibrating object. • To give a string instrument a high pitch, the string should be tight, short and thin. • To give a string instrument a low pitch, the string should be long, loose and thick. • Same principals apply to percussion and wind instruments in different applications. • End of Material for Test #1

17. Waves, Sound, Light and Optics • 16. Describe the electromagnetic spectrum. • The EM spectrum consists of light at all possible energies, frequencies and wavelengths. • All waves of the EM spectrum travel at the same speed. (speed of light) • All waves of the EM spectrum have different wavelengths and frequencies. • The EM spectrum includes gamma rays, x-rays, ultraviolet, visible, infrared, microwaves and radiowaves in order of increasing wavelength and decreasing frequency. (short to long wavelength)

18. Waves, Sound, Light and Optics • Gamma rays • *highest energy and shortest wavelengths • *wavelengths less than 10-14m • *extreme high energy, can be dangerous and may kill living cells or turn them into cancer cells. • *used to treat cancer by killing the diseased cells • *controversy surrounds the use of gamma rays in • the irradiation of food.

19. Waves, Sound, Light and Optics • X-rays • *wavelengths less than 10-8m • *commonly used in hospitals, most x-rays pass through the human body but bones and other tissues absorb a few. • Sunlight contains ultraviolet (UV) waves. • *9% of the energy emitted by the sun is UV light • *high energy, some UV light can pass through thin layers of clouds, causing you to sunburn on cloudy or overcast days

20. Waves, Sound, Light and Optics • Visible • *that portion of the EM spectrum humans can see • *commonly remembered as ROY G BIV • *red has the longest wavelength and lowest frequency (4.3 x 1014 Hz) • *violet has the shortest wavelength and highest frequency (7.5 x 1014 Hz).

21. Waves, Sound, Light and Optics • Infrared • *felt as warmth • *slightly longer than the color red, these waves warm you • *infrared lamps are used to keep food warm in a cafeteria or restaurant.

22. Waves, Sound, Light and Optics • Microwaves • *used in cooking and communication • *microwave ovens in the US use waves with a frequency of 2450 MHz (or wavelength of 12.2 cm) • *reflected by metals but are easily transmitted through air, glass, paper and plastic • *able to cook and heat food because water, fat and sugar absorb these waves and their energy; microwaves can travel about 3-5 cm into the food • *microwaves are also used in telecommunication signals

23. Waves, Sound, Light and Optics • Radio waves • *are the longest waves of the EM spectrum • *ranges in length from tenths of a meter to millions of meters. • *includes TV signals, AM and FM radio signals • *radar, used by air traffic controllers and police are also examples of radio waves

24. Waves, Sound, Light and Optics • 17. List the three theories on the nature of light. • (a) particle theory • (b) wave theory • (c) photon theory (a photon is a bundle of energy) • Scientists do NOT know exactly how to describe light.

25. Waves, Sound, Light and Optics • 18. State the speed of light in a vacuum. • 186,000 miles/second • 3 x 108 m/s, or 3 x 1010 cm/s • in a vacuum! • Slower in gases, liquids and solids because the molecules of these substance slow it down. The denser the medium, the slower light travels.

26. Waves, Sound, Light and Optics • 19. Name in order, the colors of the visible spectrum. • ROY G BIV - red, orange, yellow, green, blue, indigo, violet Waves, Sound, Light and Optics

27. Waves, Sound, Light and Optics • 20. Compare wavelength, frequency and energy for the waves of the visible spectrum. • Red : longest wavelength, lowest frequency lowest amount of energy • Violet : shortest wavelength, highest frequency, greatest amount of energy • Waves of higher frequency contain more energy.

28. Waves, Sound, Light and Optics • 21. Define and indicate examples of transparent, translucent and opaque objects. • transparent - allows most light to pass through- produces clear images. (clear smooth glass) • translucent - allows some light to pass through- produces blurry images (wax paper, frosted glass, stained glass, etc....) • opaque - blocks most light- produces no image • 22. Define reflection. • Reflection -the bouncing of a wave from a barrier.

29. Waves, Sound, Light and Optics • 23. Describe constructive interference and destructive interference of light waves. • Constructive interference occurs when two waves line up so their crests overlap. They add together to make a larger wave. • Destructive interference occurs when the crest of one wave overlaps the trough of another wave. • Subtraction occurs to produce a smaller or non-existent wave. Colors seen on soap bubbles and oils spills are due to this interference.

30. Waves, Sound, Light and Optics • 24. Name the primary, secondary and complimentary colors of light. • Primary colors of light • red, blue, green • (red + blue + green = white light) • Secondary colors • cyan, magenta, yellow • red + blue = magenta • red + green = yellow • blue + green = cyan

31. Waves, Sound, Light and Optics • Complimentary colors • Refer to a pair of colors • (one primary and one secondary) • produce white light when combined • magenta + green = white light • yellow + blue = white light • cyan + red = white light

32. Waves, Sound, Light and Optics • 25. Describe color addition and color subtraction. • Color addition if the process of combining the additive primary colors (red, blue, green) to produce other colors. • Color subtraction involves the absorption of colors to produce those that we see. • White is not a color, but the presence of all colors. Black is not a color, but the absence of all colors.

33. Waves, Sound, Light and Optics • 26. Identify the colors used in color print advertisements. • Print advertisements use the colors of yellow, cyan and magenta. A fourth "color", black is used for sharpness and contract.

34. Waves, Sound, Light and Optics • 27. Identify the colors associated with color blindness. • color-blindness - a sex linked genetic trait • people cannot “see” certain colors as others. Usually involves the colors red, green or both • cone cells of the retina do not “receive” the color and pass it through the optic nerve to the brain as they should • A totally color-blind person would see black and white and shades of gray (much like watching a black and white television).