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प्रश्न
Explain how the formation of a rainbow occurs.
Explain the phenomenon of rainbow formation in the sky. Draw the labelled ray diagram in support of your explanation.
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उत्तर
- The beautiful phenomenon of the rainbow is a combination of different phenomena, such as dispersion, refraction, and reflection of light.
- The rainbow appears in the sky after a rain shower.
- The water droplets act as small prisms.
- When sunlight enters the water droplets present in the atmosphere, they refract and disperse the incident sunlight.
- Then they reflect it internally within the droplet and finally refract it again.
- As a collective effect of all these phenomena, the seven coloured rainbows are observed.
संबंधित प्रश्न
Name the phenomenon responsible for the following effect:
When we sit in front of a plane mirror and write with our right hand, it appears in the mirror that we are writing with the left hand.
Which property of light makes a pencil cast a shadow when it is held in front of a light source?
State whether the following statement is true of false:
A student says that we can see an object because light from our eyes is reflected back by the object.
Where is the image when you look at something in a mirror?
What are the important differences between looking at a photograph of your face and looking at yourself in a plane mirror?
State the uses of plane mirrors.
A man sits in an optician's chair looking into plane mirror which is 2 m away from him and views the image of a chart which faces the mirror and is 50 cm behind his head. How far away from his eyes does the chart appear to be?
Explain how to read the following message which was found on some blotting paper:
A ray of light goes from water into air. Will it bend towards the normal or away from the normal?
State two effects caused by the refraction of light.
In which material do you think light rays travel faster-glass or air?
Name the phenomenon due to which a pencil partly immersed in water and held obliquely appears to be bent at the water surface.
- With the help of a diagram, show how when light falls obliquely on the side of a rectangular glass slab, the emergent ray is parallel to the incident ray.
- Show the lateral displacement of the ray on the diagram.
State two factors on which the lateral displacement of the emergent ray depends.
When a ray of light travelling in glass enters into water obliquely:
(a) it is refracted towards the normal
(b) it is not refracted at all
(c) it goes along the normal
(d) it is refracted away from the normal
A ray of light passes from a medium X to another medium Y. No refraction of light occurs if the ray of light hits the boundary of medium Y at an angle of:
(a) 0°
(b) 45°
(c) 90°
(d) 120°
A vertical ray of light strikes the horizontal surface of some water:
- What is the angle of incidence?
- What is the angle of refraction?
How does the light have to enter the glass:
to produce a large amount of bending?
Match the Following
| Column A | Column B |
| (a) white Light | (1) Convex mirror |
| (b) Refraction | (2) Concave mirror |
| (c) Virtual images | (3) refraction |
| (d) Real images | (4) spectrum |
| (e) Prism | (5) ray of light from glass to air |
Draw a diagram showing the refraction of a light ray from water to glass. Label on it the incident ray, the angle of incidence (/), and the angle of refraction (r)
A ray of light A incident from air suffers partial reflection and refraction at the boundary of water.
- Complete the diagram showing (i) the reflected ray B and (ii) the refracted ray C.
- How are the angles of incidence i and refraction r related?
List four characteristics of the image formed by a concave lens of focal length 20 cm when the object is placed at a distance of 40 cm from its optical centre.
The size of image of an object by a convex lens of focal length 20 cm is observed to be reduced to `1/3` rd of its size . Find the distance of the object from the optical centre of the lens .
The incident rays and refracting rays are on opposite sides of the normal.
The speed of light varies in different media.
Write scientific reason.
The sun appears on the western horizon for some time after sunset.
Write scientific reason.
A pencil appears to be broken near the surface of water.
Observe the given figure and write appropriate phenomenon of light in the box.
State whether true or false. If false, correct the statement.
The angle of deviation depends on the refractive index of the glass.
Explain with diagrams how refraction of incident light takes place from
- rarer to denser medium
- denser to rarer medium
- normal to the surface separating the two media.
The refractive index of a transparent medium is always greater than ______.
You are given water, mustard oil, glycerine and kerosene. In which of these media a ray of light incident obliquely at same angle would bend the most?
The deviation of light ray from its path when it travels from one transparent medium to another transparent medium is called ______.
In the above diagram light is travelling through different media. It is noted by a scientist that ∠1= ∠3 = ∠4 but ∠2 < ∠1. Which of the following statement would be correct?
Which surface will not reflect most of the light falling on them?
The phenomenon of light passing through the object is called ______.
The ratio of the sine of the angle of incidence to the sine of ______ is constant.
A star appears twinkling into the sky because of the reflection of light by the atmosphere.
Under what circumstances there won’t be any refraction of light when it enters from one medium to another?
