Sources of Lights
Objects that emit light on their own are called luminous objects. The light emitted by luminous objects enables us to see things around us. Examples of luminous objects are a tubelight, the sun, a lit candle, glowing bulb, a bonfire and a lit torch.
Objects that do not emit light on their own are called nonnon –luminous objects. The light emitted by luminous objects falls on non-luminous objects, and then bounces back to our eye, which enables us to see non-luminous objects. Examples of non-luminous objects are the moon, a book, a pen, a wooden box, a cupboard and a chair.
Objects through which we cannot see are called opaque objects. A medium that does not allow light to pass through it is called an opaque medium. Examples of opaque medium are a pencil box, a wooden screen, a book, a towel, a ceramic plate and chart paper.
If we are able to see anything clearly through an object, then such an object is said to be a transparent object. A medium that allows all the light incident on it to pass through it is called a transparent medium. Examples of transparent objects are plain glass, a reading glass, a plastic scale, windowpanes, a soap bubble and pure water.
Objects that allow only a part of the light incident on them to pass through it are called translucent media. Examples of translucent media are a shower stall, smoked glass, sun glasses and butter paper.
Light travels in a straight line, and its rays represent the path of light
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