Question

Why does the light reflect? What happens if we replace the opaque object with a transparent object?

Answer 1

Hint: When you look around you will find that you can see many objects or people. This is because most of the objects or surfaces are opaque. And opaque surfaces reflect the light. Something which cannot reflect the light you cannot see. Light is an electromagnetic wave. Reflection of light (and other forms of electromagnetic radiation) occurs when the waves encounter a surface or other boundary that does not absorb the energy of the radiation and bounces the waves away from the surface. The simplest example of visible light reflection is the surface of a smooth pool of water, where incident light is reflected in an orderly manner to produce a clear image of the scenery surrounding the pool.

Complete solution:
First let us understand how the reflection of light happens. We cannot see all types of light. There are different types of light. Some of them can be seen with just our eyes. For example, ultraviolet light cannot be seen with human naked eyes. But every type of radiation follows the law of reflection. The incoming light wave is referred to as an incident wave, and the wave that is bounced away from the surface is termed as the reflected wave. The visible white light that is directed onto the surface of a mirror at an angle (incident) is reflected into space by the mirror surface at another angle (reflected) that is equal to the incident angle. Thus, the angle of incidence is equal to the angle of reflection for visible light as well as for all other wavelengths of the electromagnetic radiation spectrum. This concept is often termed the Law of Reflection. It is important to note that the light is not separated into its component colors because it is not being "bent" or refracted, and all wavelengths are being reflected at equal angles. The best surfaces for reflecting light are very smooth, such as a glass mirror or polished metal, although almost all surfaces will reflect light to some degree.
Now we will analyze what happens when light incident a surface. There are two theories of light, first wave theory and second particle theory. If we think of light as a wave- when a wave incident a surface then there are two possibilities.
1. Surface bounces the wave away, or
2. Surface absorbs the light. Since electromagnetic waves are energy. It can be absorbed by some object in the form of heat. That’s why we feel an object hot when it is kept in the sunlight. But if the surface is very smooth then it reflects most of the wave. The best example is the mirror in your house. When you stand in front of the mirror the light goes from you to the mirror and it reflects back what you see as your image. Sometimes you can see your image on a transparent glass also but not that clear as on a polished mirror. That is because when you stand in front of the transparent mirror, the light which goes from you to the glass, some part of it gets reflected but more part goes through the glass.

Note: Every visible object doesn’t emit light. An object can be seen if it emits the light or it reflects the light. For example, we can see the moon but the moon itself doesn't emit light. We can also see the sun which emits light. One more important point to be noted here is that if an object or a surface appears to be red it means that the surface only reflects the red light and absorbs other color’s light.