Waves and Materials - Middle School Physical Science

1. Which interaction best models an echo from a wall: reflection, absorption, or transmission?

   Reflection. Sound bounces off hard surfaces back to the listener.

2. Which interaction is modeled when a wave hits a boundary and reverses direction in the first medium?

   Reflection. Wave bounces back without entering the second medium.

3. In a refraction model, if a wave speeds up in the second medium, does it bend toward or away from the normal?

   Away from the normal. Faster waves in new medium bend away from perpendicular.

4. What is the definition of absorption of a wave by a material?

   Wave energy is taken in by the material, often as thermal energy. Material converts wave energy to heat, reducing wave amplitude.

5. In a boundary model, which quantity stays constant when a wave crosses into a different medium: $f$, $v$, or $\lambda$?

   Frequency $f$ stays constant. Wave source determines frequency; medium changes only speed and wavelength.

6. Which interaction is modeled when light hits a rough wall and leaves in many directions?

   Scattering (diffuse reflection). Rough surfaces cause reflection in multiple random directions.

7. What is the definition of reflection of a wave at a boundary between materials?

   Wave bounces off a boundary and remains in the original medium. The wave returns to its original medium instead of passing through.

8. What is the term for a wave passing through a material instead of reflecting or being absorbed?

   Transmission. Occurs when wave energy continues through without being blocked.

9. What is refraction when a wave enters a different material?

   Wave changes speed and direction in the new material. Occurs due to different wave speeds in different materials.

10. What is the definition of refraction when a wave enters a different material?

    Wave changes speed and direction when entering a new medium. Speed change causes bending at the boundary between media.

11. What is the term for a wave changing direction as it enters a different material due to speed change?

    Refraction. Bending occurs because waves travel at different speeds in different media.

12. What is the definition of transmission when a wave meets a new material?

    Wave passes into the new material. The wave continues through the boundary into the second medium.

13. If a wave enters a new material and its speed decreases, what happens to wavelength if frequency stays constant?

    Wavelength decreases. From $v=flambda$, if $v$ decreases and $f$ is constant, $lambda$ must decrease.

14. What type of interference occurs when two crests overlap in a wave model?

    Constructive interference. Crests add together, creating larger amplitude.

15. In a boundary model, what does a larger reflected wave compared to transmitted wave indicate about the boundary?

    Large mismatch between materials; most energy is reflected. Different material properties create strong reflection.

16. Which interaction best models light passing through clear glass: transmission, absorption, or scattering?

    Transmission. Clear materials allow light to pass through unchanged.

17. Which model best represents a mechanical wave: a transverse rope wave or a light wave in vacuum?

    A transverse rope wave. Rope waves need a medium; light doesn't require one.

18. What relationship between wave speed, frequency, and wavelength should a model obey?

    $v=f\lambda$. Fundamental wave equation relating speed, frequency, and wavelength.

19. What is the term for a wave spreading out after passing through an opening or around an edge?

    Diffraction. Waves bend around obstacles due to their wave nature.

20. Which interaction is modeled when a wave passes through a narrow slit and spreads out afterward?

    Diffraction. Narrow openings cause waves to spread due to wave nature.

21. What is reflection of a wave at a boundary between two materials?

    Wave bounces back into the original material. The wave reverses direction at the interface between materials.

22. Which material interaction is best modeled by a dark surface heating up under light: reflection, absorption, or diffraction?

    Absorption. Dark surfaces absorb light energy, converting it to heat.

23. Which interaction best models water waves spreading after passing through a narrow gap: diffraction or reflection?

    Diffraction. Waves bend around edges when gap size is near wavelength.

24. If a wave enters a medium where speed decreases and frequency stays constant, what happens to wavelength?

    Wavelength decreases. Since $v = f\lambda$ and $f$ is constant, lower $v$ means lower $\lambda$.

25. What is the law relating angles in a reflection ray model (measured from the normal line)?

    Angle of incidence $=$ angle of reflection. Both angles measured from normal are equal in reflection.

26. If a wave enters a medium where speed increases and frequency stays constant, what happens to wavelength?

    Wavelength increases. Since $v = f\lambda$ and $f$ is constant, higher $v$ means higher $\lambda$.

27. What is the term for wave energy being taken in by a material and converted to thermal energy?

    Absorption. Materials convert wave energy into heat through molecular vibrations.

28. What is scattering when a wave interacts with a rough surface or particles?

    Wave spreads in many directions after interaction. Occurs when waves hit irregular surfaces or small particles.

29. What is the definition of a medium in wave models?

    Material through which a wave travels. Substance that carries wave energy from place to place.

30. Which interaction is modeled when a wave enters a new medium and bends toward the normal as it slows?

    Refraction. Bending toward normal indicates decreased speed in denser medium.

31. Which quantity stays constant when a wave changes speed entering a new medium: frequency or wavelength?

    Frequency stays constant. Source determines frequency; medium change can't alter it.

32. Identify the model feature that represents wave amplitude in a transverse wave diagram.

    Maximum displacement from the equilibrium line. Height from rest position shows energy carried by the wave.

33. What is the term for a wave bouncing off a surface and returning into the original medium?

    Reflection. Occurs when waves encounter a barrier and bounce back.

34. What is scattering when waves interact with a rough or uneven material?

    Waves reflect in many directions due to irregularities. Rough surfaces cause waves to bounce in random directions.

35. What happens to wavelength when a wave speeds up but its frequency stays the same?

    Wavelength increases. Since $v = f\lambda$ and $f$ is constant, faster $v$ means larger $\lambda$.

36. Which interaction best models why frosted glass blurs images: transmission, scattering, or refraction?

    Scattering. Irregular surface texture redirects light randomly.

37. In a ray model, what does bending toward the normal indicate about wave speed in the second medium?

    Wave speed is lower in the second medium. Waves bend toward normal when entering slower media.

38. Find the wave speed if $f=5\ \text{Hz}$ and $\lambda=2\ \text{m}$.

    $10\ \text{m/s}$. Using $v = f\lambda$: $v = 5 \times 2 = 10\ \text{m/s}$.

39. Identify the model feature that represents wavelength in a wave diagram.

    Distance between matching points (crest-to-crest or trough-to-trough). One complete wave cycle spans this distance.

40. What type of interference occurs when a crest overlaps a trough of equal amplitude in a wave model?

    Destructive interference. Opposite phases cancel out, reducing or eliminating amplitude.

41. What is the law of reflection for the angles at a reflecting surface?

    Angle of incidence equals angle of reflection. Incoming and outgoing angles are equal relative to the normal.

42. What happens to wavelength when a wave slows down but its frequency stays the same?

    Wavelength decreases. Since $v = f\lambda$ and $f$ is constant, slower $v$ means smaller $\lambda$.

43. Which type of wave requires a material medium to travel: mechanical or electromagnetic?

    Mechanical waves. Sound and water waves need matter; light doesn't.

44. What is the correct relationship among wave speed, frequency, and wavelength?

    $v=f\lambda$. Speed equals frequency times wavelength for all waves.

45. What model is commonly used to represent compressions and rarefactions in a longitudinal wave?

    A slinky (spring) model. Springs compress and stretch to show longitudinal wave motion.

46. Choose the correct model outcome: A wave enters a medium where speed is lower; what happens to wavelength?

    Wavelength decreases. Lower speed with constant frequency requires shorter wavelength.

47. Which interaction is best modeled when sound becomes quieter after passing through a thick curtain?

    Absorption (and reduced transmission). Material absorbs sound energy, reducing what passes through.

48. Which interaction is modeled when a sound wave becomes weaker after passing through thick foam?

    Absorption. Foam material converts sound energy to heat, reducing amplitude.

49. What is transmission of a wave through a material boundary?

    Wave passes into or through the new material. Some or all wave energy continues into the second material.

50. What is the law of reflection for waves at a smooth boundary?

    Angle of incidence equals angle of reflection. Fundamental principle: incoming and outgoing angles are equal.

51. What is the wave speed relationship among speed, frequency, and wavelength?

    $v = f\lambda$. Speed equals frequency times wavelength.

52. What is absorption when a wave hits a material?

    Wave energy is taken in and often converted to thermal energy. Material converts wave energy into heat or other forms.

53. Which property of a wave stays constant when it crosses into a new medium: speed, wavelength, or frequency?

    Frequency. Source determines frequency; medium changes speed and wavelength.

54. What is diffraction in terms of a wave interacting with an opening or edge?

    Wave bends and spreads around an edge or through an opening. Wave spreads out when encountering obstacles or gaps.

55. What is the term for two or more waves combining to make a new wave pattern?

    Interference. Wave amplitudes add together when waves meet.

56. In a refraction model, if a wave slows down in the second medium, does it bend toward or away from the normal?

    Toward the normal. Slower waves in new medium bend toward perpendicular.

57. Which interaction best models why sound is reduced by foam panels: reflection, absorption, or refraction?

    Absorption. Foam converts sound energy to heat, reducing noise.

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