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Questions
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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Solution
- 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.
RELATED QUESTIONS
| 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 |
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.
Write the word AMBULANCE as it would appear when reflected in a plane mirror. Why is it sometimes written in this way (as its mirror image) on the front of an ambulance?
What is the difference between regular reflection of light and diffuse reflection of light?
What type of reflection of light takes place from a cinema screen?
What is meant by 'reflection of light'?
Write all the capital letters of the alphabet which look the same in a plane mirror.
The image formed by a plane mirror is :
(a) virtual, behind the mirror and enlarged.
(b) virtual, behind the mirror and of the same size as the object.
(c) real, at the surface of the mirror and enlarged.
(d) real, behind the mirror and of the same size as the object.
The figure given alongside shows the image of a clock as seen a plane mirror. The correct time is:
Figure
(a) 2.25
(b) 2.35
(c) 6.45
(d) 9.25
A man stands 10 m in front of a large plane mirror. How far must the walk before he is 5 m away from his image?
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 ______.
Explain how to read the following message which was found on some blotting paper:
Name the phenomenon due to which a swimming pool appears less deep than it really is.
A ray of light passes from air into a block of glass. Does it bend towards the normal or away from it?
State whether the following statement is true or false:
Refraction occurs because light slows down in denser materials.
Why does a ray of light bend when it travels from one medium to another?
What is meant by the 'angle of incidence' and the 'angle of refraction' for a ray of light?
Show the lateral displacement of the ray on the diagram.
Explain with the help of a labelled ray diagram, why a pencil partly immersed in water appears to be bent at the water surface. State whether the bending of pencil will increase or decrease if water is replaced by another liquid which is optically more dense than water. Give reason for your answer.
Water is optically denser than glass.
Air is optically .......... than glass.
What do you understand by refraction of light?
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 passes from medium 1 to medium 2. Which of the following quantities of the refracted ray will differ from that of the incident ray: Speed, intensity, frequency, wavelength?
A small air bubble in a glass block when seen from above appears to be raised because of ______.
We can see the sun even when it is little below the horizon because of ______.
Light enters from air to glass having refractive index 1.50. What is the speed of light in the glass? The speed of light in vacuum is 3 × 108 m s−1.
What is atmospheric reflection? Explain with the help of a labelled diagram that the position of a star as seen by us is not its true position.
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.
Assertion and reasoning type
- Assertion: If the refractive index of the medium is high (denser medium) the velocity of the light in that medium will be small
- Reason: Refractive index of the medium is inversely proportional to the velocity of the light
What is refractive index?
If a beam of red light and a beam of violet light are incident at the same angle on the inclined surface of a prism from air medium and produce angles of refraction r and v respectively, which of the following is correct?
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 object use the reflection of light?
A water tank appears shallower when it is viewed from the top due to refraction.
Why a pencil partly immersed in water appears to be bent at the water surface.
How do twinkling stars occur? (or) what is the cause of the twinkling of stars?
The bottom of swimming pool appears to be less deep than the actual one because of
