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Question
Explain: ‘How is a rainbow formed’?
Solution
1. The beautiful phenomenon of the rainbow is a combination of different phenomena – dispersion, refraction, and reflection of light.
2. The rainbow appears in the sky after a rain shower.
3. The water droplets act as small prisms.
4. When sunlight enters the water droplets present in the atmosphere, they refract and disperse the incident sunlight.
5. Then they reflect it internally inside the droplet and finally again refract it.
6. As a collective effect of all these phenomena, the seven-colored rainbows are observed.
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| Case study: Mirage in deserts |
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To a distant observer, the light appears to be coming from somewhere below the ground. The observer naturally assumes that light is being reflected from the ground, say, by a pool of water near the tall object. Such inverted images of distant tall objects cause an optical illusion to the observer. This phenomenon is called mirage. This type of mirage is especially common in hot deserts. Based on the above facts, answer the following question: |
Which of the following phenomena is prominently involved in the formation of mirage in deserts?
| Case study: Mirage in deserts |
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| Case study: Mirage in deserts |
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The following figure shows a cross-section of a ‘light pipe’ made of a glass fiber of refractive index 1.68. The outer covering of the pipe is made of a material of refractive index 1.44. What is the range of the angles of the incident rays with the axis of the pipe for the following phenomena to occur.
