Advertisements
Advertisements
प्रश्न
Explain how spectrum is formed.
Advertisements
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.
APPEARS IN
संबंधित प्रश्न
Draw a ray diagram to show the refraction of a monochromatic ray through a prism when it suffers minimum deviation
The speed of light in glass is 2 × 105 km/s. What is the refractive index of glass?
A ray of light passes from glass into air. The angle of refraction will be:
(a) equal to the angle of incidence
(b) greater than the angle of incidence
(c) smaller than the angle of incidence
(d) 45°
Draw diagrams to show the refraction of light from
- air to glass, and
- glass to air. In each diagram, label the incident ray, refracted ray, the angle of incidence
- and the angle of refraction (r).
A monochromatic ray of light passes from air to glass. The wavelength of light in air is λ, the speed of light in air is c and in glass is V. If the absolute refractive index of glass is 1.5, write down
- the relationship between c and V,
- the wavelength of light in glass.
For which colour of white light, is the refractive index of a transparent medium the most?
A ray of light of wavelength 6600 Å suffer refraction from air to glass. Taking \[\ce{_a\mu_g = \frac{3}{2}}\], find the wavelength of light in glass.
A ray of light is passing from a transparent medium 1 to another transparent medium 2 (i) Speed up (ii) slows down. In each case, state whether the refractive index of medium 2 is equal to, less than or greater than the refractive index of medium 1.
What do you understand by the statement the refractive index of glass is 1.5 for white light?
Fill in the blanks to complete the following sentence
When light travels from a denser to a rarer medium, its speed ……………….
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 ……………….
Fig 4.31 below shows a light ray of single colour incident normally on two prisms A and B. In each case draw the path of the ray of light as it enters and emerges out of the prism. Mark the angle wherever necessary.
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
Rahim recorded the following sets of observations while tracing the path of a ray of light passing through a rectangular glass slab for different angles of incidence.
|
S. No. |
Angle of incidence |
Angle of refraction |
Angle of emergence |
|
I |
45° |
41° |
45° |
|
II |
40° |
38° |
38° |
|
III |
45° |
41° |
40° |
|
IV |
41° |
45° |
41° |
The correct observation is recorded at serial number:
(1) I
(2) II
(3) III
(4) IV
In the fig. name the ray which represents the correct path of light while passing through a glass block.
In the fig., PO is a ray of light incident on a rectangular glass block.
(a) Complete the path of the ray through the block.
(b) 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?
(c) Mark angle of emergence by the letter e. How are the angles i and e related?
(d) Which two rays are parallel to each other? Name them.
(e) Indicate in the diagram the lateral displacement between the emergent ray and the incident ray.
Fig shows a lens as a combination of a glass block and two prisms.
(i) Name the lens formed by the combination.
(ii) what is the XX' called?
(iii) Complete the ray diagram and show the path of the incident ray PQ after passing through the lens.
(iv) The final emergent ray will either meet XX' at a point or appear to come from a point on XX'. what is the point called?
In an experiment of finding the refractive index of glass, if blue light is replaced by the red light, how will the refractive index of glass change? Give reason in support of your answer.
Which colour of light travels fastest in any medium except air?
Using the curve, how do you infer that for given prism, the angle of minimum deviation δmin is unique for the given light?
How does the deviation produced by a prism depend on the wavelength of incident light?
Name the phenomenon responsible in the following case:
Twinkling of stars
Does the depth of a tank of water appear to change or remain the same when viewed normally from above?
A fish swimming in a pond seems nearer than it really is. Explain.
What is the refractive index of water
Comment on the statement ‘The refractive index of glass is 3/2.’
Name two instruments of the total refracting prism in which is used.
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 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 diagram shows the path of a ray of light through a rectangular glass block placed in a liquid of uniform density.
Show with the help of a ray diagram the path of the ray when incident ray normally falls on the first surface of the glass block and passes through the block and the liquid.
Calculate the velocity of light in a glass block of refractive index 1.5. (Velocity of light in air = 3 × 108 m/s)
A ray of light PQ is incident normally on the hypotenuse of a right-angled prism ABC as shown in the diagram given below:
(i) Copy the diagram and complete the path of the ray PQ till it emerges from the prism.
(ii) What is the value of the angle of deviation of the ray?
(iii) Name an instrument where this action of the prism is used.
