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Understanding Physics Topics is essential for solving complex problems in many fields, including engineering and medicine.
Explain in Brief About Transparent, Translucent and Opaque Objects
When light falls on a material (or object), then three things can happen : either all the light can pass through the material; or only some of the light can pass through the material; or no light can pass through the material.
So, depending on their behaviour towards light, all the materials can be classified as transparent, translucent or opaque. Let us discuss these three types of materials in somewhat detail.
1. Transparent Materials (or Transparent Objects)
Those materials which allow all the light to pass through them are called transparent materials. The materials like glass, polythene, air, water and groundnut oil are transparent materials. They allow almost all the light (which falls on them) to pass through them. We can see clearly through the transparent materials.
For example, if we look at a burning candle through a sheet of clear glass, we can see the candle and its flame clearly. This is because glass is a transparent material which allows all the light coming from the candle and its flame to pass through it. The window panes in our homes are usually made of transparent glass (see Figure).
Our spectacle glasses are also transparent. The glass tumblers in our kitchen are also transparent objects. The test-tubes, flasks and beakers in the science laboratory are also transparent objects. A car windscreen is transparent and the visor on a helmet is also transparent. The transparent objects allow all the light to pass through them due to which we can see through them clearly.
Thus, if we are able to see through an object clearly, it is allowing all the light to pass through it and hence it is a transparent object. The transparent objects allow all the light to pass through them because they do not absorb (or reflect) any light.
2. Translucent Materials (or Translucent Objects)
Those materials which allow only some of the light to pass through them are called translucent materials. In other words, light passes only partially through translucent materials. The materials like ground-glass (frosted glass), butter paper (tracing paper), oiled paper, tissue paper, sheet of white cotton, muddy water and clouds are translucent materials.
They allow only a part of the light falling on their surface to pass through them. We cannot see clearly through a translucent material.
For example, if we look at a burning candle through a piece of ground-glass (or butter paper), we can see only a dim light of the candle. We can neither see the candle itself nor the candle flame clearly through the ground-glass (which is a translucent material).
The windows of bathrooms in our homes are made of translucent material called ground-glass so that though some outside light may enter the bathroom but nothing is visible clearly from outside. Please note that we cannot see anything in detail through a translucent material. Clouds are also translucent objects.
Though we cannot see the sun through clouds on a cloudy day but still there is some sunlight all around (see Figure). This is because being translucent, clouds allow some of the sunlight to pass through them due to which there is light on earth even on a cloudy day.
Thus, if we can see through an object but not clearly, it is allowing the light to pass through it only partially and hence it is a translucent object. The translucent objects absorb (or reflect) a good part of the light falling on them and allow only some of the light to pass through them.
3. Opaque Materials (or Opaque Objects)
Those materials which do not allow any light to pass through them are called opaque materials. Tight cannot pass through opaque materials at all. The materials like cardboard, book, wooden door, metal sheet, brick wall, and stone, etc., are all opaque materials. These materials do not allow any light to pass through them. We cannot see anything through an opaque object.
For example, if we look at a burning candle through a piece of cardboard held in front of our eyes, we cannot see anything at all. This is because the cardboard (being opaque) does not allow the light of candle flame to pass through it and reach our eyes.
Similarly, we cannot see anything through a wooden door (see Figure). This is because the wooden door (or wood) is an opaque object which does not allow any light to pass through it. So, if we cannot see through an object at all, it is not allowing any light to pass through it and hence it is an opaque object. The opaque objects do not allow light to pass through them because they absorb or reflect all the light falling on them.