Sound, light, & color review answers

1. Sound, light, & color review answers CP Physics Ms. Morrison

2. 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)

3. 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

4. 2. What kind of wave is sound? • Longitudinal • mechanical

5. 3. What must an object do to produce a sound? • It must vibrate

6. 4. What is the range of frequencies humans can hear? • 20 – 20,000 Hz

7. 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

8. 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.

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

10. 8. What is the unit for loudness? • Decibel (dB) – logarithmic scale

11. 9. What are examples of resonance? • Swinging on a swing • Musical instruments • Opera singer shattering a glass • Bridge vibrations

12. 10. What is an echo? • A reflected sound wave

13. 11. What are some applications of sound? • Bats –echolocation • Sonar • Ultrasound • Seeing unborn babies • Examine heart • Uses Doppler shift

14. 12. What are the sources of vibration for the following instruments? • Brass: musician’s lips • Reed: reed • String: string against a sounding board • Other (flutes): air column within the instrument

15. 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

16. 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

17. 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

18. 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

19. 16. List the different types of electromagnetic radiation from longest wavelength to shortest wavelength. • Radio waves • Microwaves • Infrared • Visible light • Ultraviolet • X-rays • Gamma

20. 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)

21. 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)

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

23. 19. What property of electromagnetic radiation determines its energy? • Its frequency • Higher frequency = more energy • Lower frequency = less energy

24. 20. What is an example of an illuminated object? What is an example of a luminous object? • Illuminated: moon • Luminous: sun

25. 21. Describe what is happening to the light rays when they: • reflect: light bounces of boundary of a new medium • Refract: light bends as it moves from one medium into another medium (air into water) • Diffract: light passing through small opening spreads out on other side • Interfere: passing through 2 slits interferes and produces light bands (constructive) and dark bands (destructive)

26. 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

27. 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

28. 24. What are the primary light colors? • Red • Green • Blue

29. 25. What are the primary pigments? • Cyan • Magenta • Yellow

30. 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

31. 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

32. 28. What light colors make up: • Magenta light: red + blue • Yellow light: red + green • Cyan light: blue + green

33. 29. What kind of process is mixing light colors? Mixing pigments? • Light colors = additive process • Pigments = subtractive process

34. 30. How are pigments seen? • Pigments absorb some colors of light and reflect the remaining colors of light

35. 31. A white light is shown on a combination of green and blue pigments. What color is seen?

36. 32. A white light is shown on a combination of yellow and red pigments. What color is seen?

37. 33. A green light is shown on a combination of yellow and cyan pigments. What color is seen?

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

39. 35. What is seen when yellow light shines on a mixture of green and magenta pigments?

40. 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 = d v = 335 m/s t d = ? 335 = d 6.4 d = (335)(6.4) d = 2144 ÷ 2 d = 1072 m

41. 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 t d = ? 340 = d 7.2 d = (340)(7.2) d = 2448 m

42. 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 = λf f = 375 Hz 530 = λ (375) v = 530 m/s 375 375 λ = 1.41 m

43. 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

44. 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

45. 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

46. 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/s d = ? v = d/t d = vt d = (3 x 108)(3.31128 x 108) d = 9.93 x 1016 m

47. 43. How far does light travel in 180 seconds? t = 180 s v = d/t v = 3 x 108 m/s d = vt d = ? d = (3 x 108)(180) d = 5.4 x 1010 m

48. 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 m v = 3 x 108 m t = ? v = d/t t = d/v t = 1.081 x1011 3 x 108 t = 360.33 s

49. 45. What is the wavelength of a radio wave from a station whose frequency is 94.1 MHz? λ = ? v = λf f = 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

50. 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 f v = 3 x 108 m/s 620 x 10-9 620 x 10-9 f = ? f = 4.84 x 1014 Hz