Investigation 15B: Wave Interactions

Investigation 15B: Wave interactions

Waves interact with matter in four fundamental ways: reflection, refraction, diffraction, and absorption. This simulation allows you to see how each of these interactions affects waves of different frequency and wavelength.

Part 1: Investigate reflection

1.  Press [Run] to watch the waves propagate.

2.  Change the wavelength and/or frequency (using the keypad) and press [Run] to see the new simulation.

3.  Repeat the simulation for three different boundaries (or reflecting surfaces): angled wall; curved, concave wall; and curved, convex wall. Press [Run] to watch each new simulation.

Questions

a.  Sketch a continuous plane wave reflecting from a straight wall. How does the direction of the wave change?

b.  Sketch a continuous plane wave reflecting from an angled wall.

How does the direction of the wave change?

c.  Sketch a plane wave reflecting from a concave wall and a convex wall. Which one diverges the wavefronts? Which one converges the wavefronts?

concave wall convex wall

Part 2: Investigate refraction, diffraction, and interference

1.  Investigate refraction of plane waves for two cases: a flat boundary and an angled boundary.

2.  Investigate diffraction of plane waves for three cases: around a half wall and through a flat wall with single and double gaps in its middle.

3.  Investigate diffraction further by varying the wavelength for the single-gap wall.

4.  Investigate absorption using a flat boundary.

5.  Investigate interference using two circular waves.

Questions

a.  Sketch the wavefronts after refraction by the flat boundary. What happens to the direction and wavelength? What happens to the frequency (number of waves passing a point each second)?

b.  Sketch wavefronts refracted by an angled boundary.

What happens to direction and wavelength?

c.  Sketch the wavefronts for a continuous plane wave passing by a half wall. (Select Wave interaction: Diffraction) Can you describe what you observe using the term diffraction?

d.  Sketch the wavefronts passing through a flat boundary with a single gap. (Wave Interaction > Diffraction)

e.  Sketch the wavefronts passing through a flat boundary with a double gap. Describe what you observe using the term interference.

f.  How does varying the wavelength change the way the waves diffract?

g.  Sketch the wavefronts before and after interacting with the absorbing material. What happens to the wave? Propose a hypothesis to explain what happens to the energy of the wave.

before after

h.  Sketch the wavefronts for two circular waves. (Select Wave Interaction: Interference)

Where do the waves add together? Where do they cancel each other out?

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