Download Colours of the rainbow

STRAND: Space
TOPIC:
Angles
Colours of the rainbow
How often have you seen a rainbow?
A rainbow is caused by the refraction or bending of sunlight
as it passes through raindrops.
LITERACY TASK • Find the meanings of these key terms:
1. refraction: ..........................................................................................................................................................................
2. white light: .........................................................................................................................................................................
3. parallel: ..............................................................................................................................................................................
4. alternate angles: ................................................................................................................................................................
5. corresponding angles:.......................................................................................................................................................
6. co-interior angles: .............................................................................................................................................................
1. How many colours does a rainbow have?
2. Name the colours of the rainbow.
Light, such as sunlight, is called white light and is a combination of all the colours of the spectrum. When white light meets a
raindrop, it is bent, and each of the colours bends at slightly different angles causing them to separate. Red light is bent at an
angle of 42°, while at the other end of the spectrum, violet light is bent at 40°.
B
A
42°
Sunlight
D
Rain
E
C
40°
Sunlight
F
H
G
Shadow
3. All rays of sunlight are parallel. Use the diagram to find:
(a) an angle that is alternate to ∠ABG.
(b) an angle that is alternate to ∠DEG.
 John Wiley & Sons Australia, Ltd 2001
STRAND: Space
TOPIC:
Angles
INVESTIGATION: Colours of the rainbow
The diagram contains many pairs of alternate, corresponding and co-interior angles:
4. List all the pairs of alternate angles you can find in the diagram.
5. List all the pairs of corresponding angles you can find in the diagram.
6. List all the pairs of co-interior angles you can find in the diagram.
7. The angle that the rainbow appears to take in the sky is represented by ∠BGE. Explain why?
8. What is the size of ∠BGE?
9. The Moon and the Sun appear about the same size in the sky. It is well known that the Sun is many times larger than the
Moon. Explain why they appear similar.
0.5°
0.5°
10. Both the Sun and the Moon take up an angle of about 30′ (30 minutes or 1--- a degree) in the sky. How many times larger
2
than either the Sun or the Moon will the rainbow appear to be?
RESEARCH TASK ONE
You will need a clinometer.
Go out in the night sky and select a constellation. Use your clinometer to measure the angle of elevation to the
highest star in the constellation and the lowest star in the constellation. What is the angle in the sky taken up by
this constellation?
Highest star
Constellation
Lowest
star
Angles
Direct line
of sight
 John Wiley & Sons Australia, Ltd 2001