(i) Rahul was able to study the print of book due to light falling on the book which came to his eyes from a luminous object (i.e., tube light).
(ii) The light allows us to see objects.

The shadow of an aeroplane flying high in the sky is not seen on the ground because the ground will not act as screen for the aeroplane due to its high distance from the ground.

Some important properties of light are as follows:
(i) Light always travels in a straight line, which is called rectilinear propagation of light.
(ii) When light is obstructed by an opaque object, then a shadow of the object is formed behind it.
(iii) Light exhibits the property of reflection.

The two effects of light on plants are:
i) Plants use light for the preparation of their own food through the process of photosynthesis.
ii) Some plants (like sunflower) turn in the direction of light.

If we make a metal red hot, it emits light. This is called incandescent body

The light travels in a straight line path.

The dark patches formed on the ground, when light falls on the opaque objects, are called shadows.

We can see the objects around us with the help of light.

Moon doesn't produce its own light, the brightness of moon is due to the light of sun. So, it is not a luminous object.

To see a thing, there must be light which comes after reflection from the object to our eyes. In dark room there is no light, so we are not able to see our face.

Inverted and real image is formed in pinhole camera.

The material is transparent glass because only then it can pass the light through it undisturbed and the image will be formed at the same place.

Shadow of flying aeroplane cannot be seen on the earth because umbra region cannot able to reach the earth.

The image of the sun will remain same, still if we use different types of holes because the holes will act as pinhole camera and light moves in a straight path.

The name of an object which does not allow the light to pass through it is an opaque object, e.g. wood.

The light always travels in a straight line. This can be shown by performing a simple activity. For this, first of all let us take three cardboards of equal size. Now, a hole is made'at the centre of each cardboard at the same level. The three cardboard are placed on a flat table and aligned linearly as shown in the figure.
A candle is lighted at one end of the table with its flame at the level of the holes and is seen at the other end. It is observed that the light of the candle is seen effortlessly. Now, the middle one of the three cardboards is displaced from its position. Now, we are unable to see the light. The reason behind this is that the light travelling in the straight line is obstructed due the misalignment of the cardboards. This proves that light always travels in a straight line

The light from the torch C will not form a shadow on the screen because light travels in a straight path and will form the shadow on the same path from which it is coming.

(a) Richa's brother is intelligent and creative.
(b) It is true to say that shadow can mislead us. It is because the actual object cannot be verified by viewing its shadow.

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

Place the object in front of a mirror and put the light source behind the object as shown in figure.

The image/shadow will be formed by the object as well as the image of the object by mirror.