Light-Reflecting Colours

Visible light has amazing colours, and our ability to see them is amazing. The human eye can recognise more than one crore of colours.

You must have seen many colours, but have you ever wondered why some objects appear red and others blue? Why does anything have a colour? The reality is that the colour of an object is just an illusion, a red object appears red because that object cannot absorb red, and that object absorbs all other colours except red. Similarly, a blue-coloured object cannot absorb only blue colour! 

The 'white' light from the light source falls on that object. All colours except red are absorbed. Due to this, only red light reaches our eyes, and we see that object in red colour.

White Light and Its Constitutes

As we know that white colour is a mixture of all colours, the white coloured object does not absorb any colour, which makes it appear as white colour. Black colour is the opposite; black is not a colour in itself, it means the absence of colours. The black-coloured object still absorbs the colours, making it appear black.

If we throw such a light on a red object with all the other colours except red, then that object will appear black to us not red. Similarly, if you have noticed that the colour of clothes (or any other item) looks different in sunlight than in shop light. Here also, the reason is the same as almost all colours are present in sunlight, whereas some colours are absent in artificial light, due to which the absorption of colour by the fabric is different in both light.

The technical definition of colour would be something like this: "Colour is the visual effect produced from the spectral structure produced by the emission, distribution or reflection of light."

Scattering of Light

When light is incident on molecules, atoms and small particles, then it gets scattered in different directions. When sunlight, which is made up of seven colours, passes through the atmosphere, it is transmitted in different conditions by the particles present in the atmosphere. This is called the scattering of light. 

Mirror Colour

Now, have you thought about what will be the colour of the mirror? That, too, does not absorb any colour, so its colour must also be white, shouldn't it?

A mirror is an ideal surface which gives an ideal reflection. That is, the angle of the incident ray and the reflected ray are equal. But the mirror does not absorb any colour, nor does it scatter. The colour of the light of which it is incident in the mirror reflects the light of the same colour.

A Girl Seeing Herself in a Mirror.

The colour of an ideal white paper and that of an ideal mirror are the same. But there is scattering in the white paper, it is not there in the mirror, and because of this, we see the difference in the colours of both.

Reflective Colours: Which colour reflects more light? Pure white. 

Primary Colours of Light 

The main colours of light are red, green and blue. In painting, red, blue and yellow are considered the primary colours, but in Physics, the primary colours are red, blue and green. Those colours of light cannot be obtained by mixing any other colours and are independent. They are called primary colours or basic colours. There are three primary colours of light - Red, Green, and Blue. These are denoted by 'RGB'. 

Other colours are formed by mixing these three colours of light. Those colours of light that are not independent in themselves, and are obtained by mixing two primary colours are called secondary colours.

Solved Questions

1. What are the main colours of light?

Ans: The main colours of light are red, green and blue.

2. What is the colour of the mirror?

Ans: The mirror does not absorb any colour, nor does it scatter. The colour of the light of which it is incident in the mirror reflects the light of the same colour.

3. When do objects appear white and black?

Ans: An object which reflects all the optical colours appears white, and that which absorbs all the colours appears black.

Learning by Doing

Kids Activity: Surfaces That Reflect Light

For this activity, we need to arrange the following materials and follow the instructions carefully.

Materials: Torch, Mirror, a box wrapped in aluminium foil, glass jar filled with water, paper and aluminium foil ball.

Instructions:

• Give children access to the material.

• Children will use their flashlights to shine on each material.

• Children will document their observations using pictures, labels or words.

• Children will conclude other surfaces that make great reflectors of light.

Summary

Light is very important in our life. Without light, we cannot see any colour in the world. In these, we have seen how we see the colours of an object. 

As you know, in this chapter, we have studied many things related to light, including the topic of the scattering of light. Now, you must have understood the mirror's colour, an object's primary colours, and many other important things related to light.