CP Physics Ms. Morrison. Pitch: a person’s impression of a sound’s frequency Infrasonic:...

SOUND, LIGHT, & COLOR REVIEW

ANSWERS

CP PhysicsMs. Morrison

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)

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

2. What kind of wave is sound?

Longitudinal mechanical

3. What must an object do to produce a sound?

It must vibrate

4. What is the range of frequencies humans can hear?

20 – 20,000 Hz

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

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.

7. List the states of matter in order of fastest to slowest for the transmission of sound. Solids Liquids Gases

8. What is the unit for loudness?

Decibel (dB) – logarithmic scale

9. What are examples of resonance?

Swinging on a swing Musical instruments Opera singer shattering a glass Bridge vibrations

10. What is an echo?

A reflected sound wave

11. What are some applications of sound?

Bats –echolocation Sonar Ultrasound

Seeing unborn babiesExamine heartUses Doppler shift

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

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

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

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

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

16. List the different types of electromagnetic radiation from longest wavelength to shortest wavelength.

Radio waves Microwaves Infrared Visible light Ultraviolet X-rays Gamma

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)

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)

18. List the different colors of visible light from longest wavelength to shortest wavelength. Red Orange Yellow Green Blue Violet

19. What property of electromagnetic radiation determines its energy?

Its frequency Higher frequency = more

energy Lower frequency = less

energy

20. What is an example of an illuminated object? What is an example of a luminous object?

Illuminated: moon Luminous: sun

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)

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

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

24. What are the primary light colors?

Red Green Blue

25. What are the primary pigments?

Cyan Magenta Yellow

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

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

28. What light colors make up:

Magenta light: red + blue Yellow light: red + green Cyan light: blue + green

29. What kind of process is mixing light colors? Mixing pigments?

Light colors = additive process Pigments = subtractive process

30. How are pigments seen?

Pigments absorb some colors of light and reflect the remaining colors of light

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

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

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

34. What is seen when blue light shines through a cyan filter?

R G B

C

Color seen is BLUE

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

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

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

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

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

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

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

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

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

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

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

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

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