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प्रश्न
Glass is transparent in nature. Why does glass powder look opaque? When water is poured over it, it again becomes transparent. Why?
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उत्तर
In the case of powdered glass, irregular reflection takes place from various particles. Thus, light is sent back into the same medium. Therefore, it looks opaque. On putting water over the powder incident light gets refracted through water. That is why it looks transparent.
संबंधित प्रश्न
Study the following four experimental set-ups I, II, III and IV for the experiment, "To trace the path of a ray of light through a rectangular glass slab."
Which of the marked set-ups is likely to give best results (P1 and P2 are the positions of pins fixed on the incident ray)?
(A) I
(B) II
(C) III
(D) IV
Write a relationship between the angle of incidence and angle of refractions for a given pair of media.
Observe the following figure and answer the questions given under it:
1) How many times does refraction take place in the above figure?
2) What happens to the ray of light when it passes from air to glass?
3) What happens to the ray of light when it passes from glass to air?
4) What are the rays AB and CD in the figure called?
5) Define refraction.
The refractive index of glass is 1.5. From a point P inside a glass block, draw rays PA, PB and PC incident on the glass air surface at an angle of incidence 30°, 42° and 60° respectively.
- In the diagram show the approximate direction of these rays as they emerge out of the block.
- What is the angle of refraction for the ray PB?
`("Take" sin 42° =2/3)`
“A ray of light incident on a rectangular glass slab immersed in any medium emerges parallel to itself.” Draw labelled ray diagram to justify the statement.
Define the term refractive index of a medium. What do you understand by the statement 'the refractive index of glass is 1.5 for white light'?
Why is the colour red used as a sign of danger?
State the relation between the refractive index μ and the velocity of light (vm) in that medium.
In the diagram below, PQ is a ray of light incident on a rectangular glass block.
Copy the diagram and complete the path of the ray of light through the glass block. In your diagram, mark the angle of incidence by letter ‘i’ and the angle of emergence by the letter ‘e’.
Explain with the help of a diagram of how fish is able to see the objects above it.
