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प्रश्न
Explain how spectrum is formed.
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उत्तर
When white light passes through a glass prism, it spreads out into a band of different colours called the spectrum of light.
- When white light is dispersed into seven colours by a glass prism, different colours bend through different angles with respect to the incident ray.
- The sequence of colours given by the prism is Violet, Indigo, Blue, Green, Yellow, Orange and Red.
- Of the seven colours, red light bends the least, while violet light bends the most. So, the rays of each colour emerge along different paths and appear distinct. Hence, we get a spectrum of seven different colours.
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संबंधित प्रश्न
When rays of light are incident on a glass slab then the incident ray and emergent ray are _________ each other.
- perpendicular
- parallel
- opposite
- concurrent
Define refraction and state the laws of refraction.
A student traces the path of a ray of light passing through a rectangular glass slab and marks the angle of incidence i, angle of refraction r and angle of emergence e, as shown.
The correctly marked angle(s) is/are
(A) ∠ i only
(B) ∠ e only
(C) ∠ r only
(D) ∠ i and ∠ e
Explain the term absolute refractive index of a medium and write an expression to relate it with the speed of light in vacuum.
Which colour of light travels fastest in any medium except air?
Draw the diagram of refraction of light in the glass slab
Light of a single colour is passed through a liquid having a piece of glass suspended in it. On changing the temperature of liquid, at a particular temperature the glass piece is not seen. When is the glass piece not seen?
How does the angle of minimum deviation produces by a prism change with increase in :
the refracting angle of prism?
The diagram alongside shows the refraction of a ray of light from air to a liquid.
- Write the values of (i) angle of incidence, (ii) angle of refraction.
- Use Snell’s law to find the refractive index of liquid with respect to air.
Name the colour of white light which is deviated the most on passing through a prism.
What is meant by the statement the critical angle for diamond is 24°?
The refractive index of air with respect to glass is expressed as `""_g μ_a=sin i /sin r`.
- Write down a similar expression for aμg in terms of the angles i and r.
- If angle r = 90°, what is the corresponding angle i called?
- What is the physical significance of the angle i in part (b)?
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 total reflecting right angled isosceles prism can be used to deviate a ray of light through:
(a) 30° (b) 60° (c) 75° (d) 90°.
Which of the following is the best experimental set-up out of the four shown for tracing the path of a ray of light passing through a rectangular glass slab ?
While performing the experiment on tracing the path of a ray of light through a rectangular glass slab, in which of the following experimental set-ups is a student likely to get best results? P1 and P2 are the positions of pins fixed by him.
(A) I
(B) II
(C) III
(D) IV
-
- the angle of refraction and
- the angle of deviation for the ray?
The critical angle for glass-air interface is :
Name the phenomenon responsible in the following case:
Twinkling of stars
What is the refractive index of vacuum
Express the refractive index μ of a medium in terms of the velocity of light.
In what condition a prism is said to be in the position of minimum deviation? What is the direction of the refracted ray inside the prism in this condition?
You are provided with a printed piece of paper. Using this paper how will you differentiate between a convex lens and a concave lens?
The refractive index of air with respect to glass is defined: as gµa = sin i/sin r
If r = 90°, what is the corresponding angle i called?
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’.
A ray of monochromatic light is incident from air into a glass slab. Draw a labelled ray diagram indicating the change in its path till it emerges out of the slab. In the diagram, mark the angle of incidence (i) and the angle of refraction (r) at the first interface. How is the refractive index of glass related to the angles i and r?
The figure shows two prisms A and B. A monochromatic ray of light PO is incident at the face of the prism A. Complete the diagram to show the path of the ray till it emerges out of the prism B.
Draw a diagram to show the refraction of a monochromatic light ray through an equilateral prism. On the diagram, label the incident, refracted, and emergent rays. It also indicates the angle of deviation by the letter δ.
Calculate the velocity of light in a glass block of refractive index 1.5. (Velocity of light in air = 3 × 108 m/s)
A glass block is having refractive index 3/2, the light ray is incident at an angle 45°. Find the sine of the angle of, refraction inside the glass block.
The diagram below shows two parallel rays A (Orange) & B (Blue) incident from air, on air-glass boundary.
- Copy and complete the path of the rays A and B.
- How do the speeds of these rays differ in glass?
- Are the two refracted rays in glass parallel? Give a reason.
A ray of light strikes the surface of a rectangular glass slab such that the angle of incidence in air is
- 0°,
- 45°.
In each case, draw a diagram to show the path taken by the ray as it passes through the glass slab and emerges from it.
