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प्रश्न
Answer the following question in detail.
Explain the formation of a secondary rainbow. For which angular range with the horizontal is it visible?
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उत्तर
- A ray AB incident from Sun (white light) strikes the lower portion of a water drop at an incident angle i.
- On entering into the water, it deviates and disperses into constituent colours. The figure shows the extreme colours (violet and red).
Formation of secondary rainbow - Refracted rays BV and BR finally emerge the drop from V' and R' after suffering two internal reflections and can be seen by an observer on the ground.
- Minimum deviation rays of red and violet colour are inclined to the ground level at θR ≈ 51° and θV ≈ 53° respectively. As a result, in the rainbow, the violet is above and red is below.
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संबंधित प्रश्न
Fill in the blank:
Very fine particles mainly scatter ………… colored light.
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\[1 \cdot 2\] Both the surfaces of the lens are convex. If it is dipped into water (μ = 1.33), it will behave like
A concave mirror having a radius of curvature 40 cm is placed in front of an illuminated point source at a distance of 30 cm from it. Find the location of the image.
A concave mirror forms an image of 20 cm high object on a screen placed 5.0 m away from the mirror. The height of the image is 50 cm. Find the focal length of the mirror and the distance between the mirror and the object.
A concave mirror has a focal length of 20 cm. Find the position or positions of an object for which the image-size is double of the object-size.
A point source S is placed midway between two converging mirrors having equal focal length f as shown in figure. Find the values of d for which only one image is formed.
Locate the image of the point P as seen by the eye in the figure.
k transparent slabs are arranged one over another. The refractive indices of the slabs are μ1, μ2, μ3, ... μk and the thicknesses are t1 t2, t3, ... tk. An object is seen through this combination with nearly perpendicular light. Find the equivalent refractive index of the system which will allow the image to be formed at the same place.
An optical fibre (μ = 1.72) is surrounded by a glass coating (μ = 1.50). Find the critical angle for total internal reflection at the fibre-glass interface.
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A container contains water up to a height of 20 cm and there is a point source at the centre of the bottom of the container. A rubber ring of radius r floats centrally on the water. The ceiling of the room is 2.0 m above the water surface.
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- Find the maximum value of r for which the shadow of the ring is formed on the ceiling. Refractive index of water = `4/3`.
A biconvex thick lens is constructed with glass (μ = 1.50). Each of the surfaces has a radius of 10 cm and the thickness at the middle is 5 cm. Locate the image of an object placed far away from the lens.
Fill in the blank and rewrite the completed statement:
Very fine particles mainly scatter ______ light.
Answer the following question in detail.
State the conditions under which a rainbow can be seen.
Answer the following question in detail.
Explain the formation of a primary rainbow. For which angular range with the horizontal is it visible?
Answer the following question in detail.
Is it possible to see primary and secondary rainbow simultaneously? Under what conditions?
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State any one difference between a primary rainbow and a secondary rainbow.
| 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: |
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.
The sky would appear red instead of blue if
Between the primary and secondary rainbows, there is a dark band known as Alexandar’s dark band. This is because ______.
- light scattered into this region interfere destructively.
- there is no light scattered into this region.
- light is absorbed in this region.
- angle made at the eye by the scattered rays with respect to the incident light of the sun lies between approximately 42° and 50°.
