New
New
Year 11
Edexcel
Foundation

# Refraction through a rectangular block

I can describe what refraction is and draw accurate ray diagrams of refraction.

New
New
Year 11
Edexcel
Foundation

# Refraction through a rectangular block

I can describe what refraction is and draw accurate ray diagrams of refraction.

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## Lesson details

### Key learning points

1. Refraction is when waves travel from one transparent medium to another, causing a change in direction.
2. When waves slow down, they turn towards the normal line (angle of incidence > angle of refraction).
3. When waves speed up, they turn away from the normal line (angle of incidence < angle of refraction).
4. Refraction can be investigated using a clear rectangular block, ray box and narrow slit, pencil, paper and a protractor.
5. The greater the angle of incidence, the greater the angle of refraction.

### 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.

### Content guidance

• Equipment requiring safe usage.

### 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).

## Starter quiz

### 6 Questions

Q1.
What is represented by an arrow in a ray diagram?
a peak of a wave
a trough of a wave
the edge of a wave
Correct answer: the direction of wave travel
Q2.
Which of the following statements about light is correct?
Light cannot change direction.
Correct answer: All types of wave can be reflected.
A ray box produces a single ray of light.
Light can only reflect from shiny surfaces.
Q3.
Match the key words (relating to how light interacts with different objects) to their definitions.
Correct Answer:absorbed,taken in and loses energy inside the material of the object

taken in and loses energy inside the material of the object

Correct Answer:transmitted,passes through the material of the object

passes through the material of the object

Correct Answer:reflected,bounces off the surface of the object

bounces off the surface of the object

Q4.
In a ray diagram, the ray that approaches a surface or boundary is called the ray.
Q5.
The ray diagram shown represents a light wave hitting a mirror. Which of the following diagrams shows the normal line (represented by a dashed line) drawn correctly?
Correct Answer: An image in a quiz
Q6.
The ray diagram shown is for a light wave reflecting from a mirror. A student has placed a protractor over the diagram. What is the angle of incidence?
27°
77°
117°
123°

## Exit quiz

### 6 Questions

Q1.
Which of the following words describe what can happen when light hits an object?
rarefaction
Q2.
What is refraction?
a wave splitting when it meets a boundary
Correct answer: a wave changing direction when it crosses a boundary
a wave changing direction by bouncing back from a boundary
Q3.
The ray diagram represents a light wave passing from one medium to another. The normal is drawn as a dashed line. A student has placed a protractor over the diagram. What is the angle of refraction?
29°
79°
119°
121°
Q4.
The ray diagram shows the refraction of a light wave when it crosses a boundary between two materials. Which of these statements are correct?
Correct answer: The angle of refraction is less than the angle of incidence.
The angle of refraction is greater than the angle of incidence.
Correct answer: When the ray crosses the boundary, it bends towards the normal.
When the ray crosses the boundary, it bends away from the normal.
Q5.
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?
Correct answer: The angle of refraction is always smaller than the angle of incidence.
Correct answer: 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.
Q6.
Which of these ray diagrams shows a possible path of a ray through a plastic block?
Correct Answer: An image in a quiz