Science [3 Marks Each] QUE-ANS

A shadow is a dark outline or image cast by an opaque object that blocks light coming from a source of light. It is formed when light hits the opaque object which does not let the light pass through. Everywhere else around the opaque object, the light continues in a straight path until it bounces off the ground or wall behind the object. The wall or ground behind the opaque object is the screen. On this screen is a dark patch, or shadow, with the same outline as the object surrounded by light. The colour of the opaque object does not affect the colour of the shadow that is formed.

If we are able to see clearly through an object, it is said to be transparent.
Example: Glass and water. There are some objects through which we can see but not clearly. Such objects are known as translucent objects.
Example: Tracing paper. If we cannot see through an object at all, it is an opaque object.
Example: Wood, plastic box etc.

We can see the objects through air clearly, means we can observe all the objects in their original shapes and sizes without any disturbance, it means the environment around us which is just air, must be transparent.
But when thick smoke, thick clouds, etc., are present in the air, it does not remain transparent.

An image is formed due to reflection of light by a plane mirror. In a completely dark room, there is no light present in the room. Thus, no reflection of light takes place by the mirror placed in the room. Hence, no image will get formed by a mirror in a completely dark room.

The shadow of an object cannot be caught if the screen and the object are very far from each other. This is the same case. Here, also the shadow of the football cannot be seen on the ground (which acts as a screen) when it is kicked high in the air.
This happens because if we take the object away and away from the screen, the shadow becomes smaller and smaller in size and a time comes when it totally disappears from the screen.

Colours of the shirts will remain same. We see them on the screen because pinhole camera forms the image of the object having same colour but upside down.
So, yellow shirt will form yellow image and red shirt will form red image.

Shadow of an object does not change on changing its colour. Shadow will always show the absence of light at that place. So, the colour of shadow will remain same in all the cases. Thus, the shadows of all the towels are black in colour.

When a cylinder is held in sunlight, then a circular shadow or a rectangular shadow can be obtained depending on its orientation related to the Sun.

When the top of the cylinder faces the Sun, then the shadow formed is circular. On the other hand, when the side of the cylinder faces the Sun, then the shadow formed is rectangular.

Transparent: Glass and water.
Opaque: Wood and plastic box.
Translucent: Fog and smoke.

Yes, the shadow will be formed in each case but in all the cases, the darkness of the shadow will be different.

1. Most of the light in case of transparent sheet of glass will pass through the glass. So, the darkness of shadow will be very low.
2. Most of the light in case of muslin cloth will be reflected. So, the shadow will be darker than the transparent sheet of glass.
3. While in case of plywood, all the light would be stopped completely by the plywood. So, the darkness strength will be highest in this case.

No, they do not cast any shadow on the ground because they are very high in the sky. They can cast shadow only if they are at some lower height, i.e. if they are near to the ground, we can see their shadows.

A small circular image of the sun will be obtained in all the three cases because the holes will act as a pinhole camera, whatever be their shapes. Also, as the light moves in a straight path, therefore the image of the sun will remain same.

Shadow is just an absence of light at that place. Shadow is not affected by the colours of the object because the amount of light preventing to pass will remain same.
The shadow is affected by the shape of the object only. If the object is large, the shadow will be large and vice-versa.

Transparent glass sheet can be made translucent by two ways:

1. By rubbing it on the ground and making it rough.
2. By applying oil, grease or butter on it.