Physics
Answer
If an opaque object is placed in front of a point source of light, it obstructs the passage of light and produces a dark patch on a screen placed behind the object. This dark patch is called the shadow of the opaque object.
The shadow is formed because light from the source travels in straight lines.
Related Questions
How is the image affected in a pin hole camera when another fine hole is made near the first pin hole ?
State the effect on the image in a pin hole camera if:
(a) the hole is made bigger.
(b) the luminous object is moved towards the pin hole.
(c) the length of the pin hole camera is increased (i.e. the screen is moved away from the pin hole).
State two differences between an umbra and a penumbra.
Why is it that the birds flying in the sky do not cast their shadows on the earth ?