Advertisements
Advertisements
Question
Answer the following question in detail.
Explain the formation of a primary rainbow. For which angular range with the horizontal is it visible?
Advertisements
Solution
- A ray AB incident from Sun (white light) strikes the upper portion of a water drop at an incident angle i.
- On entering into the water, it deviates and disperses into constituent colours. The figure shows the extreme colours (violet and red).
Formation of primary rainbow - Refracted rays BV and BR strike the opposite inner surface of water drop and suffer internal reflection.
- These reflected rays finally emerge from V′ and R′ and can be seen by an observer on the ground.
- For the observer, they appear to be coming from the opposite side of the Sun.
- Minimum deviation rays of red and violet colour are inclined to the ground level at θR = 42.8° ≈ 43° and θV = 40.8 ≈ 41° respectively. As a result, in the rainbow, the red is above and violet is below.
APPEARS IN
RELATED QUESTIONS
Give a scientific reason:
Danger signal lights are red in colour.
Why can’t we see clearly through fog?
Why does unpolarised light from a source show a variation in intensity when viewed through a polaroid which is rotated?
Show with the help of a diagram, how unpolarised light from Sun gets linearly polarised by scattering.
Draw the intensity distribution for the fringes produced in interference ?
Draw the intensity distribution for the diffraction bands produced due to single slit ?
Why does the Sun look reddish at sunset or sunrise ?
In the meterbridge experimental set up, shown in the figure, the null point ‘D’ is obtained at a distance of 40 cm from end A of the meterbridge wire. If a resistance of 10Ω is connected in series with R1, null point is obtained at AD = 60 cm. Calculate the values of R1 and R2.
Describe briefly using a diagram how sunlight is polarised ?
Suppose you are inside the water in a swimming pool near an edge. A friends is standing on the edge. Do you find your friend taller or shorter than his usual height?
The image formed by a concave mirror
A parallel beam of light is incident on a converging lens parallel to its principal axis. As one moves away from the lens on the other side on its principal axis, the intensity of light
A convex lens is made of a material having refractive index
\[1 \cdot 2\] Both the surfaces of the lens are convex. If it is dipped into water (μ = 1.33), it will behave like
A concave mirror having a radius of curvature 40 cm is placed in front of an illuminated point source at a distance of 30 cm from it. Find the location of the image.
A concave mirror forms an image of 20 cm high object on a screen placed 5.0 m away from the mirror. The height of the image is 50 cm. Find the focal length of the mirror and the distance between the mirror and the object.
A candle flame 1.6 cm high is imaged in a ball bearing of diameter 0.4 cm. If the ball bearing is 20 cm away from the flame, find the location and the height of the image.
Light is incident from glass (μ = 1.50) to water (μ = 1.33). Find the range of the angle of deviation for which there are two angles of incidence.
A point source is placed at a depth h below the surface of water (refractive index = μ). (a) Show that light escapes through a circular area on the water surface with its centre directly above the point source. (b) Find the angle subtended by a radius of the area on the source.
A paperweight in the form of a hemisphere of radius 3.0 cm is used to hold down a printed page. An observer looks at the page vertically through the paperweight. At what height above the page will the printed letters near the centre appear to the observer?
Answer the following question in detail.
State the conditions under which a rainbow can be seen.
Answer the following question in detail.
Explain the formation of a secondary rainbow. For which angular range with the horizontal is it visible?
Rainbow is the phenomenon due to ______.
A plano-convex lens is made of material having refractive index 1.5. The radius of curvature of curved surface is 40 cm. The focal length of the lens is ____________ cm.
State any one difference between a primary rainbow and a secondary rainbow.
| Case study: Mirage in deserts |
 |
|
To a distant observer, the light appears to be coming from somewhere below the ground. The observer naturally assumes that light is being reflected from the ground, say, by a pool of water near the tall object. Such inverted images of distant tall objects cause an optical illusion to the observer. This phenomenon is called mirage. This type of mirage is especially common in hot deserts. Based on the above facts, answer the following question: |
Which of the following phenomena is prominently involved in the formation of mirage in deserts?
| Case study: Mirage in deserts |
 |
|
To a distant observer, the light appears to be coming from somewhere below the ground. The observer naturally assumes that light is being reflected from the ground, say, by a pool of water near the tall object. Such inverted images of distant tall objects cause an optical illusion to the observer. This phenomenon is called mirage. This type of mirage is especially common in hot deserts. Based on the above facts, answer the following question : |
A diver at a depth 12 m inside water `(a_(µω) = 4/3)` sees the sky in a cone of semi-vertical angle
Between the primary and secondary rainbows, there is a dark band known as Alexandar’s dark band. This is because ______.
- light scattered into this region interfere destructively.
- there is no light scattered into this region.
- light is absorbed in this region.
- angle made at the eye by the scattered rays with respect to the incident light of the sun lies between approximately 42° and 50°.
