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प्रश्न
Write scientific reason.
The sun appears on the western horizon for some time after sunset.
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उत्तर
- As ray of light from the Sun enters the earth’s atmosphere, it follows a curved path due to refraction, before reaching the observer.
- This makes the apparent position of the Sun slightly higher than the actual position for the observer.
- Hence, due to the atmospheric refraction of sunlight, the observer on the earth continues to see the setting Sun for two minutes after the Sun has dipped below the horizon, thus delaying the sunset.
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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, if appears in the mirror that we are writing with the left hand.
Where is the image when you look at something in a mirror?
A ray of light strikes a plane mirror such that its angle of incidence is 30°. What angle does the reflected ray make with the mirror surface?
What are the important differences between looking at a photograph of your face and looking at yourself in a plane mirror?
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?
An extended object in the form of an arrow pointing upward has been placed in front of a plane mirror. Draw a labelled ray-diagram to show the formation of its image.
Define the following terms used in the study of reflection of light by drawing a labelled ray-diagram:
(a) Incident ray
(b) Point of incidence
(c) Normal
(d) Reflected ray
(e) Angle of incidence
(f) Angle of reflection
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.
An object is placed 20 cm in front of a plane mirror. The mirror is moved 2 cm towards the object. The distance between the positions of the positions of the original and final images seen in the mirror is ______.
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 from a rarer medium to a denser medium, will it bend towards the normal or away from it?
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?
In which material do you think light rays travel faster-glass or air?
Fill in the following blank with suitable word:
Light bends when is passes from water into air. We say that it is ............
What is meant by 'refraction of light'? Draw a labelled ray diagram to show the refraction of light.
What is meant by the 'angle of incidence' and the 'angle of refraction' for a ray of light?
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.
With the help of a labelled diagram, explain why a tank full of water appears less deep than it actually is.
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 when passes from glass to air, bends towards the normal.
The speed of light is more in glass than in water.
What is the cause of refraction of light when it passes from one medium to another?
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.
Lights of different colours are used as signal for safety transport. From these, the wavelength of red light is _______ nm.
The speed of light varies in different media.
Write scientific reason.
The bottom of a pond appears raised.
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.
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 ______.
What is refractive index?
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 surface will not reflect most of the light falling on them?
Why a pencil partly immersed in water appears to be bent at the water surface.
