New
New
Year 11
OCR
Higher

# 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.

New
New
Year 11
OCR
Higher

# 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.

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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. 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.

### 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.
In a wavefront diagram, what does a wavefront show?
a beam of light
Correct answer: a peak of a wave
the front of a wave
the frequency of a wave
the direction of wave travel
Q2.
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.
Correct answer: All types of wave can be reflected.
Q3.
Match the terms with their meanings.
Correct Answer:absorbed,loses its brightness as it passes through the object

loses its brightness as it passes through the object

passes through 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.
This ray diagram represents a light wave hitting a mirror. Which diagram shows the normal line drawn correctly (as a dashed line)?
Correct Answer: An image in a quiz
Q6.
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°
77°
117°
123°

## Exit quiz

### 6 Questions

Q1.
What is the angle of refraction?
29°
79°
119°
121°
Q2.
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?
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.
Q3.
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.
Q4.
Which of these ray diagrams shows a possible path of a ray through a plastic block?
Correct Answer: An image in a quiz
Q5.
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.
Correct answer: The speed of light is higher in air than in glass.
Correct answer: As a wavefront crosses the boundary, the section that is in air travels faster.
Correct answer: The change in speed makes the wavefront rotate.
Q6.
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?
Correct Answer: An image in a quiz