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Source

These slides are intended as a waves revision lesson with (no EM covered)

The sources and ideas are explained more fully in the post,

If useful in teaching, please comment here.

Choose three words to define

AbsorbDisplacementEmitMediumParallelPerpendicularTransmit

WavesBest of 3

LOs

To check understanding and use of key words

To practise drawing ray diagrams

How It Works

Each slide has a question or statement and three possible responses.

These can be good, okay or wrong.

Choose the best response(s) and aim to explain what makes it better. How could you improve the other choices?

Waves…

… transfer energy and movement through a material.

… transfer energy without permanent movement of the material.

… transfer material without permanent movement of energy.

Waves…

… transfer energy and movement through a material.

… transfer energy without permanent movement of the material.

… transfer material without permanent movement of energy.

Longitudinal Waves…

… have displacement parallel to the movement of the wave.

… travel faster than all transverse waves.

… include sound and pressure waves.

Longitudinal Waves…

… have displacement parallel to the movement of the wave.

… travel faster than all transverse waves.

… include sound and pressure waves.

The wave equation is…

v = f x λ

f = v / λ

λ = v / f

The wave equation is…

v = f x λ

f = v / λ

λ = v / f

v = 4m/s, λ = 2m

f = 4 x 2 = 8 Hz

f = 4 / 2 = 2 Hz

f = 2 / 4 = 0.5 Hz

v = 4m/s, λ = 2m

f = 4 x 2 = 8 Hz

f = 4 / 2 = 2 Hz

f = 2 / 4 = 0.5 Hz

Waves like light…

… reflect at a boundary; incident and reflected angles are equal.

… refract at a boundary; refraction is towards the normal when entering a denser material.

… refract at a boundary; refraction is away from the normal when leaving a denser material.

Waves like light…

… reflect at a boundary; incident and reflected angles are equal.

… refract at a boundary; refraction is towards the normal when entering a denser material.

… refract at a boundary; refraction is away from the normal when leaving a denser material.

Refraction happens…

…only when the wave is travelling along the normal.

…every time a wave reaches a boundary

…only when the wave speed is different in the two materials.

Refraction happens…

…only when the wave is travelling along the normal.

…every time a wave reaches a boundary.

…only when the wave speed is different in the two materials.

Water waves…

…speed up in deeper water.

…slow down in shallower water.

…travel at the same speed no matter how deep the water.

Water waves…

…speed up in deeper water.

…slow down in shallower water.

…travel at the same speed no matter how deep the water.

Diffraction …

… happens whenever a wave travels through a narrow gap.

… means the wave front bends when travelling through a gap or past an object.

… works best with gaps and objects of the same size as the wavelength.

Diffraction …

… happens whenever a wave travels through a narrow gap.

… means the wave front bends when travelling through a gap or past an object.

… works best with gaps and objects of the same size as the wavelength.

Showing Waves

We can show the wave front as if seen from above, but often draw a line showing the direction of travel.

From Wikicommons From dev.physicslab.org

Drawing ray diagrams

1. Start with a sharp pencil and ruler.

2. Draw objects, mirrors and blocks clearly.

3. Draw a straight line, with a ruler, from where the light starts to where it finishes.

4. Use an arrow to show direction of travel.

5. Angles of reflection and refraction should be approximately right but not usually measured.

From ScienceBlogs

Practice

Draw a diagram of refraction in a glass block, labelling: Incident ray Normal Angle of incidence Refracted ray Angle of refraction