Date: September 26, 2020
104: Refraction
Starter Activity: 5 minutes
Observe the straw in the glass of water. Can you see where the
straw appears to break?
Copy down this definition of refraction:
Refraction is how a ray of light bends as it passes from one
medium (a substance) to another, due to a change in its speed
Homework: Test 1: Light, lessons 101 - 105
• 104 Refraction of Light Practical October 4
Unit 2: Light SCF: Self-Confidence
Lesson Outcomes: By the end of the lesson,…
… all students will be able to:
Accurately draw and state what happens when light passes from air to glass
… most students will be able to:
Explain why this happens
… some students will be able to:
Predict what will happen to light when it travels from one substance to another with a
different refractive index
Unit 2: Light SCF: Self-Confidence
1 When Light Bends
… all students will be able to:
Accurately draw and state what happens when light passes from air to glass
Unit 2: Light SCF: Self-Confidence
1 When Light Bends
Is it easier to run on the road, or to run through deep mud?
… all students will be able to:
Accurately draw and state what happens when light passes from air to glass
Unit 2: Light SCF: Self-Confidence
1 When Light Bends
… most students will be able to:
Explain why this happens
Unit 2: Light SCF: Self-Confidence
1 When Light Bends
… most students will be able to:
Explain why this happens
Unit 2: Light SCF: Self-Confidence
1 When Light Bends
The speed of light depends on the material through which the light is travelling. When light
enters a different material (e.g. when moving from air into glass), the speed of light changes.
This causes the light to bend or refract.
air
glass
The speed of light is affected by the density of the material through which it is travelling.
When light enters a more dense medium, its speed decreases and this is why
refraction (bending of light) occurs.
Now, write out what happens when light leaves a dense medium and enters a less
dense medium.
… most students will be able to:
Explain why this happens
Unit 2: Light SCF: Self-Confidence
2 Investigating Refraction
Complete the Form: 104 Refracting Light and submit it to me now.
Now, copy this results table into your Exercise book:
Angle of incidence/ ° Angle of refraction/ °
20
40
60
80
Extension:
Test 1: Light, lessons 101 - 105
October 4
… some students will be able to:
Predict what will happen to light when it travels from one substance to another
Unit 2: Light SCF: Self-Confidence
2 Investigating Refraction
Now, use the ray box to investigate refraction.
• First, lay the block so that the top left corner fits into the corner
on the diagram. Trace around the outside of the glass block. 20°
Remove the block.
• Now draw a line at 20° to the left of the normal line so that it
just strikes the block outline.
• Shine the ray of light along this line.
• Mark where the light comes out of the block on the other side.
Then remove the block.
• Find and draw the path the light traveled through the block.
• Measure the angle of refraction – FROM THE NORMAL!
• Complete the same ray diagram for angles of incidence
equal to 40°, 60°, and 80°.
Test 1: Light, lessons 101 - 105
October 4
… some students will be able to:
Predict what will happen to light when it travels from one substance to another
Unit 2: Light SCF: Self-Confidence
3 Follow-up
Now, draw a graph of your results, following the guidance I show you on my graph…
Test 1: Light, lessons 101 - 105
October 4
… some students will be able to:
Predict what will happen to light when it travels from one substance to another
Unit 2: Light SCF: Self-Confidence
Plenary
Copy and answer this question: What happens when the incident ray travels along the
normal into a glass block?
Test 1: Light, lessons 101 - 105
October 4
… some students will be able to:
Predict what will happen to light when it travels from one substance to another
Unit 2: Light SCF: Self-Confidence
Unit 2: Light SCF: Self-Confidence
