Rectilinear Propagation And Reflection Of Light

Rectilinear Propagation of Light

How does light travel? If you stand up on a mountain you can see around you for miles and miles, how are you able to do that? This article will answer your questions on the propagation of light, more specifically the rectilinear propagation of light. Have you seen a light house by the beach? The lights on a light house rotate around the light house so that it is visible from all sides. Why can’t we see a light house if the light isn’t rotating?

You will understand the propagation of light with a simple experiment. Place a candle on a table and light it. Place three cardboard sheets blocking your view of the candle. In these cardboard sheets make three pinholes at equal heights such that the flame of the candle is visible through the cardboard sheets. Now view the flame through the holes, you’ll find it visible. Now move one of the cardboard sheets and try to see the flame. Can you? On moving the cardboard sheet, you will see that the flame is no longer visible. Now bring the sheets back in line. The flame is visible again.

Rectilinear Propagation

The light is visible only when all the three pinholes are aligned proving the rectilinear propagation of light

From this experiment, we can deduce that light moves from place to place through rectilinear propagation. Rectilinear is a fancy word for straight. Light travels from the source in a straight line. Let’s examine another characteristic of light; The Reflection of Light.

Reflection of Light

Have you ever seen your reflection in a still surface of a lake? Surely, you must have seen a mirror. Why can we see our reflection on some surfaces and not others? Reflection of light is referred to the change in the direction of light upon striking a surface. This change in direction occurs whenever light hits a surface, irrespective of the texture or the nature of the surface.

Rectilinear Propagation

Reflection of light from a surface

So what is the difference between a mirror and a wall? In lay man’s terms, reflection is dependent on the smoothness of the reflecting surface. For you to see your reflection, the reflection of light has to occur uniformly. For example, if you throw a ball at a rough surface it will bounce in a random direction. Similarly, the reflection of light on a rough surface is also random which does not lead to the formation of a clear reflection. This is though you can see your face in a steel plate, it is not as clear as a mirror.

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Practise This Question

In AM, the centpercent modulation is achieved when