Seasons: part 1
Classroom Activity for 14-16
In this demonstration, a lamp and piece of paper are used to show how the light from the Sun is spread out more on the surface of the Earth when it strikes the Earth at an angle.
Apparatus and Materials
- Large piece of card
- Board to which card can be fixed
- Lamp with cardboard cylinder
- Two different coloured marker pens
Health & Safety and Technical Notes
- This demonstration can also be done as a class practical, as the equpiment used is quite common in schools.
- The cardboard cylinder is placed around the end of the lamp so that a rougly circular area of light is projected on the card
- The demonstration shows that when light hits a surface at an angle it is spread out over a greater area than if it strikes the surface perpendicularly. Any energy transfer is therefore spread over a greater area.
- To compare the difference in area, it is easy to draw a line around the area where the light falls when the card is perpendicular to the light source, and when it is at an angle.
- In addition, it is possible to use a light sensor to show that the intensity of the light falling in each area is different.
- In place of the card, a photocopied map could be used to make the demonstration look more like a part of the Earth's surface.
- Some students may find it difficult to relate a flat piece of card to the curved surface of a planet.
- This demonstration leads directly into Seasons- Part 2