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प्रश्न
Explain with the help of a diagram of how fish is able to see the objects above it.
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उत्तर
A fish can see everything above it in clear water irrespective of its position in different depths. The critical angle for water is 48.5°. The angle of the cone of vision for the fish is twice this angle.
Hence it is 97°. All the objects outside water but in this cone of vision Will be seen by the fish. Outside this range, the fish will see all the objects in the surrounding area (see figure). Those objects which are at the bottom will be seen by the fish due to total internal reflection taking place at the water-air interface.
संबंधित प्रश्न
In your laboratory you trace the path of light rays through a glass slab for different values of angle of incidence (∠i) and in each case measure the values of the corresponding angle of refraction (∠r) and angle of emergence (∠e). On the basis of your observations your correct conclusion is:
(a) ∠i is more than ∠r, but nearly equal to ∠e
(b) ∠i is less then ∠r, but nearly equal to ∠e
(c) ∠i is more than ∠e, but nearly equal to ∠r
(d) ∠i is less than ∠e, but nearly equal to ∠r
Fill in the blanks to complete the following sentence
The refractive index of glass with respect to air is 3/2. The refractive index of air with respect to glass will be ……………….
Select from the following the best experimental set-up for tracing the path of a ray of light through a glass slab:
(A) I
(B) II
(C) III
(D) IV
Comment on the statement ‘The refractive index of glass is 3/2.’
Explain briefly what causes the twinkling of stars at night.
How does the angle of deviation produced by a prism depend on the colour of light used? Which colour of white light is deviated (i) most, (ii) least, by a prism?
You are provided with a printed piece of paper. Using this paper how will you differentiate between a convex lens and a concave lens?
How does the angle of deviation produced by a prism depend on the angle of incidence of light at the prism surface? Draw a graph to illustrate your answer.
A ray of monochromatic light is incident from the air on a glass slab:
(i) Draw a labelled ray diagram showing the change in the path of the ray till it emerges from the glass slab.
(ii) Name the two rays that are parallel to each other.
(iii) Mark the lateral displacement in your diagram.
The speed of light in air is 3 × 108 ms-1. Calculate the speed of light in water. The refractive index of water is 4/3.
