We all are familiar with light and its importance. Light is such an important source that without it all colourful things would have been black for us. So let us see how we can define such an important source. Light is a form of energy that enables us to see around us or we can say that it is an electromagnetic wave that can travel through any medium as well as through vacuum.
Types of objects
There are two types of objects as follows -
Luminous objects
Luminous Objects: They are those which have their own light. We can see
them as they have their own light. When their light reaches our eyes that is
the time when we can see them. For example we have sun, tube light, etc. It
is not necessary that it should possess light naturally. If any substance
glows on passing current, that also falls under the same category.
Non Luminous objects
Non Luminous Objects: They are those which do not have their own light. So,
if there is no light, we can’t see them. To see, we need a luminous object
around it. For example: furniture, walls, moon, etc.
when light falls on any surface, either of these phenomena takes place:
- Light falling on a surface: It may get absorbed. The surface that absorbs all the light falling on it appears to be black in colour, or in other words we say that black is a good absorber and emitter of light.
- When light falls on the surface it may pass through it. But it is not that all light rays would pass. Certain substances allow all rays to pass and few substances allow only certain rays to pass. Those substances which allow all rays to pass appear to be transparent. The process of allowing rays to pass through is called transmit process. For example: glass is transparent as it allows all rays to pass through it. In this figure we have tinted a plane glass. You can easily notice that tinted glass allows only a few rays to pass and on the other hand, plane glass allows all rays to pass through it.
