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Transcript of CP Physics Ms. Morrison. Pitch: a person’s impression of a sound’s frequency Infrasonic:...
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SOUND, LIGHT, & COLOR REVIEW
ANSWERS
CP PhysicsMs. Morrison
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1. Define the following sound vocabulary terms: Pitch: a person’s impression of a sound’s
frequency Infrasonic: sounds below 20 Hz Ultrasonic: sounds above 20,000 Hz Compression: high pressure region of the
sound wave, medium pushed together Rarefaction: low pressure region of the
sound wave, medium spreads out Loudness: a person’s impression of sound
intensity (proportional to wave’s amplitude)
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1. Define the following sound vocabulary terms: pg 2 Forced vibration: vibration of an object
caused by contact with another vibrating object
Natural frequency: frequency at which minimum energy needed to make the material of the object vibrate and requires the least amount of energy to continue the vibrations
Resonance: when the forced vibration of an object matches its natural frequency and causes a dramatic increase in the amplitude
Beat: difference between the frequencies of two sounds heard together
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2. What kind of wave is sound?
Longitudinal mechanical
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3. What must an object do to produce a sound?
It must vibrate
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4. What is the range of frequencies humans can hear?
20 – 20,000 Hz
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5. What is the speed of sound at 0 oC? At 20 oC?
Speed of sound at 0 oC = 331 m/s
Speed of sound at 20 oC = 343 m/s
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6. What happens to the speed of sound if the air temperature gets hotter? It increases – this is because the
particles move faster and faster and transfer the wave energy more quickly.
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7. List the states of matter in order of fastest to slowest for the transmission of sound. Solids Liquids Gases
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8. What is the unit for loudness?
Decibel (dB) – logarithmic scale
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9. What are examples of resonance?
Swinging on a swing Musical instruments Opera singer shattering a glass Bridge vibrations
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10. What is an echo?
A reflected sound wave
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11. What are some applications of sound?
Bats –echolocation Sonar Ultrasound
Seeing unborn babiesExamine heartUses Doppler shift
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12. What are the sources of vibration for the following instruments?
a. Brass: musician’s lipsb. Reed: reedc. String: string against a sounding
boardd. Other (flutes): air column within
the instrument
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13. How does the interference of sound waves make sounds louder or softer?
Constructive interference – in phase – causes sound to become louder
Destructive interference – out of phase – causes sound to become softer
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14. Why do you see an airplane before you hear its engines?
The speed of light is one million times faster than the speed of sound.
343 m/s vs. 3 x 108 m/s
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15. Define the following light and color vocabulary terms: Transparent: material transmits light
through it (can see through it) Translucent: material scatters the light it
transmits (can see light but not through it, frosted windows)
Opaque: material does not transmit light, cannot see through it or see light through it
Quantum theory: energy given off as bundles of light energy called photons, explains how light interacts with matter
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15. Define the following light and color vocabulary terms: pg2 Dual theory: light moves through space
as a wave and interacts with matter as a particle
Luminous: object gives off light, ex. Sun, lights, fire flies
Illuminated: object reflects light, ex. Moon, mirror
Photon: particle of light energy
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16. List the different types of electromagnetic radiation from longest wavelength to shortest wavelength.
Radio waves Microwaves Infrared Visible light Ultraviolet X-rays Gamma
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17. List the seven types of electromagnetic radiation and describe them and their uses.
Radio waves: radio and TV (longest λ, lowest frequency, and least energy)
Microwaves: heating food Infrared: heat waves, used in heat
lamps, night vision goggles, remotes Visible light: smallest part of EM
spectrum, colors of light Ultraviolet: causes skin damage –
sunburns, can kill bacteria (on fruits and vegetables)
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17. List the seven types of electromagnetic radiation and describe them and their uses. pg 2
X-rays: used to see teeth and bones for medical purposes, airport security
Gamma rays: used for radiation therapy, given off in nuclear explosions (shortest λ, highest frequency, most energy)
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18. List the different colors of visible light from longest wavelength to shortest wavelength. Red Orange Yellow Green Blue Violet
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19. What property of electromagnetic radiation determines its energy?
Its frequency Higher frequency = more
energy Lower frequency = less
energy
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20. What is an example of an illuminated object? What is an example of a luminous object?
Illuminated: moon Luminous: sun
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21. Describe what is happening to the light rays when they:
a. reflect: light bounces of boundary of a new medium
b. Refract: light bends as it moves from one medium into another medium (air into water)
c. Diffract: light passing through small opening spreads out on other side
d. Interfere: passing through 2 slits interferes and produces light bands (constructive) and dark bands (destructive)
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22. When does light behave like a particle? Give examples.
Photosynthesis Absorb light to create electric
current (solar calculators) Absorb light energy then release as
color of light
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23. What is polarization of light? How can one determine if a material is polarized? Light can only pass through in one
direction – parallel to material’s polarizing axis
Use polarized filter and turn 90o to see if light is blocked out
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24. What are the primary light colors?
Red Green Blue
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25. What are the primary pigments?
Cyan Magenta Yellow
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26. What are complementary colors? List the primary light colors and their complements.
Two colors that produce white light when they are added together (primary light color + secondary light color)
Red + Cyan Green + Magenta Blue + Yellow
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27. When do you see white light? When do you see black?
White light is seen when all colors reflected
Black is seen when all colors absorbed
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28. What light colors make up:
Magenta light: red + blue Yellow light: red + green Cyan light: blue + green
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29. What kind of process is mixing light colors? Mixing pigments?
Light colors = additive process Pigments = subtractive process
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30. How are pigments seen?
Pigments absorb some colors of light and reflect the remaining colors of light
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31. A white light is shown on a combination of green and blue pigments. What color is seen?
R G B
G
B
Color seen is BLACK
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32. A white light is shown on a combination of yellow and red pigments. What color is seen?
R G B
Y
R
Color seen is RED
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33. A green light is shown on a combination of yellow and cyan pigments. What color is seen?
R G B
Y
C
Color seen is GREEN
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34. What is seen when blue light shines through a cyan filter?
R G B
C
Color seen is BLUE
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35. What is seen when yellow light shines on a mixture of green and magenta pigments?
R G B
G
M
Color seen is BLACK
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36. A person yells across a canyon and hears his echo 6.4 seconds later. If the speed of sound is 335 m/s, how wide is the canyon?
t = 6.4 s v = dv = 335 m/s td = ? 335 = d
6.4d = (335)(6.4)d = 2144 ÷ 2 d = 1072 m
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37. Thunder is heard 7.2 seconds after a bolt of lightning is observed. If the speed of sound is 340 m/s, how far away did the lightning strike?
t = 7.2 s v = d v = 340 m/s td = ? 340 = d
7.2d = (340)(7.2)d = 2448 m
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38. What is the wavelength of a sound wave that has a frequency of 375 Hz and a speed of 530.0 m/s?
λ = ? v = λff = 375 Hz 530 = λ (375)v = 530 m/s 375 375
λ = 1.41 m
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39. An ambulance is moving at a velocity of 25 m/s as it approaches the bus stop. The ambulance’s siren has a frequency of 325 Hz. What does a person sitting at the bus stop perceive the siren’s frequency to be?
vs = 25 m/s f’ = f (v + vd)
f = 325 Hz (v – vs)
vd = 0 m/s f’ = 325 (343 + 0)
v = 343 m/s (343 – 25)f’ = ? f’ = 325 (1.08)
f’ = 351 Hz
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40. A woman on a train traveling at 32 m/s. The train passes a factory whose whistle is blowing at 288 Hz. What frequency does the woman hear as the train approaches the factory?
vs = 0 m/s f’ = f (v + vd)
f = 288 Hz (v – vs)
vd = 32 m/s f’ = 288 (343 + 32)
v = 343 m/s (343 – 0)f’ = ? f’ = 288 (1.09)
f’ = 313.92 Hz
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41. What is the beat frequency between two tuning forks if one has a frequency of 520 Hz and 528 Hz?
528 – 520 Hz = 8 Hz
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42. How far away is a star from Earth, if its light takes 10.5 years to reach Earth?
10.5 yrs (365d/y)(24h/d)(3600 s/h) = 3.31128 x 108 s = t
v = 3.0 x 108 m/sd = ? v = d/t
d = vtd = (3 x 108)
(3.31128 x 108)d = 9.93 x 1016 m
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43. How far does light travel in 180 seconds?
t = 180 s v = d/tv = 3 x 108 m/s d = vtd = ? d = (3 x 108)
(180)d = 5.4 x 1010 m
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44. How long does it take light from the sun to reach Venus? Venus is 1.081 x 1011 m from the sun?
d = 1.081 x 1011 mv = 3 x 108 mt = ? v = d/t
t = d/vt = 1.081 x1011 3 x 108 t = 360.33 s
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45. What is the wavelength of a radio wave from a station whose frequency is 94.1 MHz?
λ = ? v = λff = 94.1 MHz 3 x 108 = λ (94.1
x 106) = 94.1 x 106 Hz 9.41 x 106 94.1
x 106
v = 3 x 108 m/s λ = 3.19 m
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46. What is the frequency of a light wave with a wavelength of 620 nm?
λ = 620 nm v = λf = 620 x 10-9 m 3 x 108 = 620 x
10-9 fv = 3 x 108 m/s 620 x 10-9 620 x
10-9 f = ? f = 4.84 x 1014
Hz
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47. A light wave has a wavelength of 4.90 x 10-7 m. What is its frequency?
v = λfλ = 4.90 x 10-7 m 3 x 108 = 4.9 x 10-
7 fv = 3 x 108 m/s 4.9 x 10-7 4.9 x 10-
7 f = ? f = 6.12 x 1014
Hz