LIGHT AND SHADOW
A shadow is made when an object blocks light. The shadow appears the side of the object furthest from the light source. The object must be opaque or translucent to make a shadow. A transparent object will not make any shadow, as light will pass straight through it. Opaque object make dark shadows. Translucent objects make faint shadows.
Transparent materials let light pass through them in straight lines, so that you can see clearly through them. Glass is an example of a transparent material.
Translucent materials let some light through, but they scatter the light in all directions, so that you cannot see clearly through them. Tissue paper is an example of a translucent material.
Opaque materials do not let any light pass through them. They block the light. Iron stick is an example of an opaque material.
If an object is moved closer to the light source, the shadow gets bigger.
If an object is moved further away from the light source, the shadow gets smaller.
1. We can investigate the Earth's rotation by observing the length and position of a shadow.
2. While the Earth rotates from the west to the east, the east part of the Earth gets the sunshine earlier than the west.
3. This makes the Sun appears to rise from the east in the morning in the middle of the sky at midday, and sets in the west at dusk.
4. If an object is places in an open space, the length the position of the shadow changes from the west to the east.
5. The changes of the length and the position of the shadow from the west to the east shows that the Earth rotates from the west to the east.