Question

Short note on Shadow.

Answer 1

1. Shadow is a dark patch formed behind an opaque object when it is placed in the path of light.
2. A shadow is formed only when a light source, an opaque object and a screen are present, e.g. during a lunar eclipse we see a part of the earth’s shadow on the surface of the moon.
3. This happens when the earth, the sun, and the moon are in a straight line with the earth between sun and the moon.
4. Here the sun acts as the light source, the earth as the opaque object and moon as the screen.
5. Shadows are formed due the rectilinear propagation of light.
6. The size and the shape of the shadow depend on the position and orientation of the opaque object between the source of light and the screen.
7. If the distance of the object from the source is decreased, then the size of the shadow increases.
8. If the object is moved away from the source, then the size of the shadow decreases.
9. In older days shadows caused by objects placed in the sun were used to measure time. Such a device is called sun dial.