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प्रश्न
Lights of different colours are used as signal for safety transport. From these, the wavelength of red light is _______ nm.
पर्याय
400
500
600
700
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उत्तर
Lights of different colours are used as signal for safety transport. From these, the wavelength of red light is 700 nm.
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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 |
Which property of light makes a pencil cast a shadow when it is held in front of a light source?
The letter F is placed in front of a plane mirror:
- How would its image look like when seen in a plane mirror?
- What is the name of the phenomenon involved?
Which type of reflection of light leads to the formation of images?
State the uses of plane mirrors.
Define the following terms used in the study of reflection of light by drawing a labelled ray-diagram:
- Incident ray
- Point of incidence
- Normal
- Reflected ray
- Angle of incidence
- Angle of reflection
The image in a plane mirror is virtual and laterally inverted. What does this statement mean?
If a ray of light goes from a rarer medium to a denser medium, will it bend towards the normal or away from it?
When a light ray passes from air into glass, what happens to its speed? Draw a diagram to show which way the ray of light bends.
With the help of a labelled diagram, explain why a tank full of water appears less deep than it actually is.
State two factors on which the lateral displacement of the emergent ray depends.
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.
Light travelling from a denser medium to a rarer medium along a normal to the boundary:
(a) is refracted towards the normal
(b) is refracted away from the normal
(c) goes along the boundary
(d) is not refracted
How does the light have to enter the glass:
to produce a large amount of bending?
How does the light have to enter the glass:
for no refraction to happen?
A ray of light when passes from glass to air, bends towards the normal.
The depth of a pond when seen from above appears to be less.
Water is optically .......... than 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)
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.
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.
The laws of reflection hold true for ______.
The speed of light varies in different media.
Write a scientific reason.
The coin disappears in a vessel as it is seen from a specific location. But as soon as the water is poured into the vessel to a certain level, the coin appears.
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?
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?
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.
Light travels fastest in a vacuum. Why?
A water tank appears shallower when it is viewed from the top due to refraction.
Which is optically denser out of the two medium M1& M2 having the refractive indices = 1.71 and 1.36 respectively?
How do twinkling stars occur? (or) what is the cause of the twinkling of stars?
Match the following:
| Column I | Column II | ||
| 1. | r > 90 | a. | Light gazes at the surface of separation between the two modes. |
| 2. | r = 90 | b. | No refraction. |
| 3. | r < 90 | c. | Refracted ray away from the normal |
The bottom of swimming pool appears to be less deep than the actual one because of
