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Question
Describe an experiment to show that light travels in a straight-line path.
Solution
Take three cardboards A, B, and C each about 25 cm square. Take a pin and make a small hole in each cardboard at the same height. Suspend the cardboard pieces by separating threads vertically from support so that each hole is at the same height, as shown. Pass a string through the holes and pull it taut. This makes the three holes in a straight line. Now, take out the string.
Place a lighted candle near one of the cardboards (say A). Look at the candle flame from the other side of the cardboard. C. The candle flame is seen.
Now, slightly displace one of the cardboards (say B) so the holes no longer remain straight. Again, look at the candle flame from the other side of the cardboard C. You do not see the candle flame. The reason is that light travels in a straight line, and now the holes in the cardboards A, B, and C are not straight.
Conclusion: Light travels in a straight line path called rectilinear light propagation.
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RELATED QUESTIONS
What do you mean by ‘rectilinear propagation of light’?
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Name a simple application of the rectilinear propagation of light
Match the following
| 1. | Rectilinear propagation | Primary source of light |
| 2. | Plane Mirror | Non-luminous object |
| 3. | Fire fly | Periscope |
| 4. | The Moon | Pinhole camera |
| 5. | Wide light source | Spectrum of light |
| 6. | Regular reflection | luminous object |
| 7. | The sun | Penumbra |
| 8. | Band of seven colors | Glossy surface |
Light shows ______.
Rectilinear propagation is ______.
