Pearson Edexcel · GCSE · Physics
Course version: 1PH0 · Version from Sept 2016
4.9P Describe the effects of a reflection b refraction c transmission d…
Full specification wording
Topic 4 – Waves: 4.9P Describe the effects of a reflection b refraction c transmission d absorption of waves at material interfaces
At a boundary between two materials a wave can be reflected, refracted, transmitted or absorbed, and this point asks you to describe each effect.
Checked against the Pearson Edexcel 1PH0 specification (opens in a new tab) on .
- Point 9 of 15
Study notes
From the checked teaching notes for this specification point.
The idea
At a boundary between two materials a wave can be reflected, refracted, transmitted or absorbed, and this point asks you to describe each effect. Reflection sends the wave back into the first material, with the angle of incidence equal to the angle of reflection, as when light bounces off a mirror. Refraction bends the wave as its speed changes on entering the new material, for example light slowing and bending towards the normal when it passes from air into glass. Transmission lets the wave carry on into the second material, often with a change of speed and direction. Absorption transfers the wave's energy to the material, raising its temperature, as a dark surface warms in sunlight.
What earns the marks
- Describes reflection as the wave returning into the original material with the angle of incidence equal to the angle of reflection.
- Describes refraction as a change in speed at the boundary causing a change in direction of the wave.
- Describes transmission as the wave passing into the second material, possibly with a change of speed or direction.
- Describes absorption as energy being transferred from the wave to the material, often raising its temperature.
Common mistakes and how to put them right
Confuses refraction with reflection.
Put it right: Refraction involves a change of speed and direction as the wave enters a new material.
States that a transmitted wave always keeps the same speed.
Put it right: Note that its speed can change at the interface.
Describes absorption as the wave bouncing back.
Put it right: Absorption transfers energy into the material instead.
Exam tips
- Name the interface and the two materials when describing each effect.
- Link refraction to a change of wave speed, not just a change of direction.
- For absorption, state where the wave's energy goes, such as heating the material.
Try the lesson
The start of the Topic 4 – Waves: 4.9P Describe the effects of a reflection b refraction c transmission d absorption of waves at material interfaces lesson, made from checked teaching notes for this specification point.
Have a go first
A black cloth left in sunlight becomes warm. Which effect of the light waves at the cloth's surface causes this warming?
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