Starter quiz
- In a wavefront diagram, what does a wavefront show?
- a beam of light
- a peak of a wave ✓
- the front of a wave
- the frequency of a wave
- the direction of wave travel
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- Which statement about light is correct?
- Light cannot change direction.
- A ray box produces a single ray of light.
- Light can only reflect from shiny surfaces.
- All types of wave can be reflected. ✓
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- Match the terms with their meanings.
- absorbed⇔loses its brightness as it passes through the object ✓
- transmitted⇔passes through the object ✓
- reflected⇔bounces off the surface of the object ✓
- In a ray diagram, the ray that approaches a surface or boundary is called the ______ ray.
- 'incident' ✓
This ray diagram represents a light wave hitting a mirror. Which diagram shows the normal line drawn correctly (as a dashed line)?
The ray diagram represents a light wave reflecting from a mirror. A student has placed a protractor over the diagram. What is the angle of incidence?- 27°
- 63° ✓
- 77°
- 117°
- 123°
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Exit quiz
What is the angle of refraction?- 29°
- 61° ✓
- 79°
- 119°
- 121°
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The ray diagram shows the refraction of a light wave when it crosses a boundary between two materials. Which of these statements are correct for light at a boundary from air into a transparent block?- The angle of refraction is less than the angle of incidence. ✓
- The angle of refraction is greater than the angle of incidence.
- When the ray crosses the boundary, it bends towards the normal. ✓
- When the ray crosses the boundary, it bends away from the normal.
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A student measures the angle of incidence and the angle of refraction at a boundary from air into a transparent block. The table shows the results. Which of these statements are correct?- The angle of refraction is always smaller than the angle of incidence. ✓
- The greater the angle of incidence, the greater the angle of refraction. ✓
- When the angle of incidence doubles, the angle of refraction doubles.
- The angle of refraction increases by the same amount as the angle of incidence.
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- Which of these ray diagrams shows a possible path of a ray through a plastic block?
The diagram represents the refraction of a light wave as it passes from glass into air. It shows rays and wavefronts. Which of the statements are correct?- The wavelength is shorter in air than in glass.
- The speed of light is higher in air than in glass. ✓
- As a wavefront crosses the boundary, the section that is in air travels faster. ✓
- The change in speed makes the wavefront rotate. ✓
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- A light wave travels from a medium in which it is slower into a medium in which it is faster. The vertical black line shows the boundary between the two media. Which diagram is correct?
Worksheet
Presentation
Video
Lesson Details
Key learning points
- Refraction is when waves travel from one transparent medium to another, causing a change in direction.
- When waves slow down, they turn towards the normal line (angle of incidence > angle of refraction).
- When waves speed up, they turn away from the normal line (angle of incidence < angle of refraction).
- Refraction can be investigated using a clear rectangular block, ray box and narrow slit, pencil, paper and a protractor.
- Refraction occurs when one side of a wavefront enters the new medium before the other, causing a change in wave speed.
Common misconception
Pupils sometimes rote-learn what specific examples of refraction look like, rather than developing a more general understanding of the direction waves turn based on changes in wave speed.
Teach pupils the general theory of refraction and apply it to a variety of different examples where wave speed changes (e.g. sound waves refract in the opposite direction to light at an air-glass boundary due to the different wave speeds).
Keywords
Refraction - Refraction occurs when waves travel from one transparent medium to another, causing a change in wave speed and direction.
Normal - The normal is an imaginary line drawn at 90° to a surface.
Angle of incidence - The angle of incidence is the angle between the incident ray and the normal.
Angle of refraction - The angle of refraction is the angle between the refracted ray and the normal.
Wavefront - Wavefronts are lines drawn to represent the peaks of a wave.