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प्रश्न
Explain how the formation of a rainbow occurs.
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उत्तर
- The beautiful phenomenon of the rainbow is a combination of different phenomena – 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.
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Then they reflect it internally inside the droplet and finally again refract it.
- As a collective effect of all these phenomena, the seven coloured rainbows are observed.
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संबंधित प्रश्न
| Column I | Column II | Column III | |
| 1 | Dispersion | Long-sightedness | Twinkling of stars |
| 2 | Refraction | Splitting of white light into component colours | Convex lens |
| 3 | Hypermetropia | Change in the direction of the ray of light due to change in medium | Spectrum of seven colours |
Name the phenomenon responsible for the following effect:
When we sit in front of a plane mirror and write with our right hand, if appears in the mirror that we are writing with the left hand.
If an object is placed at a distance of 10 cm in from of a plane mirror, how far would it be from its image?
What type of reflection of light takes place from a cinema screen?
The boy walks towards the mirror at a speed of 1 m/s. At what speed does his image approach him?
With the help of a labelled ray-diagram, describe how a plane mirror forms an image of a point source of light placed in front of it. State the characteristics of the image formed in a plane mirror.
The image of an object formed by a plane mirror is:
(a) virtual
(b) real
(c) diminished
(d) upside-down
A ray of light strikes a plane mirror PQ at an angle of incidence of 30°, is reflected from the plane mirror and then strikes a second plane mirror QR placed at right angles to the first mirror. The angle of reflection at the second mirror is ______.
If a ray of light goes form a denser medium to a rarer medium, will it bend towards the normal or away from the normal?
When a ray of light passes from air into glass, is the angle of refraction greater than or less than the angle of incidence?
Fill in the following blank with suitable word:
Light bends when is passes from water into air. We say that it is ............
A coin in a glass tumbler appears to rise as the glass tumbler is slowly filled with water. Name the phenomenon responsible for this effect.
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°
How does the light have to enter the glass:
to produce a large amount of bending?
Draw suitable diagrams to illustrate how a beam of light incident parallel to the principal axis is reflected by:
(a) a concave mirror, and (b) a convex mirror
The diagram (figure) given below shows two parallel rays 1 and 2 incident on (a) a concave mirror, (b) a convex mirror. Draw the reflected rays and mark the focus by the symbol F.
A light ray suffers reflection and refraction at the boundary in passing from air to water. Draw a neat labelled ray diagram to show it.
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?
The phenomenon of change in the direction of light when it passes from one transparent medium to another is called ___________.
Light changes its direction when going from one transparent medium to another transparent medium. This is called _______.
Identify the wrong figure from the following.
The speed of light varies in different media.
Write scientific reason.
The bottom of a pond appears raised.
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.
Numerical problems.
The speed of light in water is 2.25 × 108 ms–1. If the speed of light in vacuum is 3 × 108 ms–1, calculate the refractive index of water.
Noor, a young student, was trying to demonstrate some properties of light in her Science project work. She kept ‘X’ inside the box (as shown in the figure) and with the help of a laser pointer made light rays pass through the holes on one side of the box. She had a small butter-paper screen to see the spots of light being cast as they emerged.
Her friend noted the following observations from this demonstration:
- Glass is optically rarer than air.
- Air and glass allow light to pass through them with the same velocity.
- Air is optically rarer than glass.
- Speed of light through a denser medium is faster than that of a rarer medium.
- The ratio: sin of angle of incidence in the first medium to the ratio of sin of angle of refraction in the second medium, gives the refractive index of the second material with respect to the first one.
Which one of the combinations of the above statements given below is correct.
Which object use the reflection of light?
When light passes from one medium to another the ray gets bent. This property of light is called ______.
How does the light travel?
The bending of light as it passes from one medium to another is called ______.
A ray of light traveling in medium 1 strikes and travels into another transparent medium 2. If the speed of light is greater in medium 1, the ray will ______.
The ratio of the sine of the angle of incidence to the sine of ______ is constant.
Light is refracted or bent while going from one medium to another because of its ______ changes.
A water tank appears shallower when it is viewed from the top due to refraction.
Assertion: The air bubble shines in water.
Reason: Air bubble shines due to the refraction of light.
When a ray of light travels normal to the given surface, then the angle of refraction is ______.
