Refraction through a rectangular block (including wave front diagrams)
I can describe what refraction is, draw accurate diagrams of refraction and use the idea of wavefronts to explain what causes refraction.
Refraction through a rectangular block (including wave front diagrams)
I can describe what refraction is, draw accurate diagrams of refraction and use the idea of wavefronts to explain what causes refraction.
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.
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.
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).
Content guidance
- Risk assessment required - equipment
Supervision
Adult supervision required
Licence
This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).
Lesson video
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Starter quiz
6 Questions
loses its brightness as it passes through the object
passes through the object
bounces off the surface of the object
Exit quiz
6 Questions
