The path of light
How does light travel?
* Have you ever seen the scene of
light penetrating through the branches of trees in denser forest?
* Have you ever seen the path of sun
light entering through the hole of a cement grill building?
* Have you ever seen the path of a
laser light?
ACTIVITY 1
Requirement: Three empty match
boxes, pin, candle and wooden blocks.
Procedure: Arrange empty match
boxes and wooden blocks as shown in the figure. First, you make a hole
in the inner tray of each match box such that all three holes are in the same
spot. Arrange the match boxes as shown in figure. Now, adjust the three inner
trays in such a way that the three holes are in a straight line. Place a
lighted candle at one end of this arrangement and try to see the flame of
candle from a hole at the other end. Is the flame visible?
Now, arrange the trays
such a way that they are not at the same height. Try to see the flame. Is it
visible? What does this activity tell you about the path of light?
Light travels in straight
line, it cannot bend the path itself. This is called as the rectilinear
propagation of light. This is one of the most important property of light.
Al-hasan -Haytham was ascientific thinker who made important contribution
to the understanding of vision, optics and light. He observed that light coming
through a tiny hole travelled in straight lines and projected an image onto the
opposite wall. Based on such experimentation, he concluded that vision is accomplished
by rays coming from external luminous sources and entering the eye, rather than
through rays emitted from the eye as was then commonly believed. He is the
first one to experiment with light and found important properties like the rectilinear
propagation of light.
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