Question

name the thing which are always necessary to observe a shadow ​

Answer 1

Answer:

Solution: (a) Sun is not always necessary to observe a shadow because any source of light, an opaque object and a screen are just necessary enough to see a shadow.

Answer 2

Answer:

To cast a shadow you need an object that can block light rays. Not every object is able to do that. Some materials will let the light pass through whereas others will only block some of it. Objects able to block all the light are called opaque and will form a shadow.