Advertisements
Advertisements
प्रश्न
Answer the following question in detail.
Explain the formation of a primary rainbow. For which angular range with the horizontal is it visible?
उत्तर
- 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
संबंधित प्रश्न
Why can’t we see clearly through fog?
Name the phenomenon responsible for it.
Draw the intensity distribution for the fringes produced in interference ?
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.
What is linearly polarized light?
Describe briefly using a diagram how sunlight is polarised ?
A thin lens is made with a material having refractive index
\[\mu = 1 \cdot 5\]. Both the side are convex. It is dipped in water \[\mu = 1 \cdot 33\]. It will behave like
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 1 cm object is placed perpendicular to the principal axis of a convex mirror of focal length 7.5 cm. Find its distance from the mirror if the image formed is 0.6 cm in size.
k transparent slabs are arranged one over another. The refractive indices of the slabs are μ1, μ2, μ3, ... μk and the thicknesses are t1 t2, t3, ... tk. An object is seen through this combination with nearly perpendicular light. Find the equivalent refractive index of the system which will allow the image to be formed at the same place.
Light falls from glass (μ = 1.5) to air. Find the angle of incidence for which the angle of deviation is 90°.
The diameter of the sun is 1.4 × 109 m and its distance from the earth is 1.5 × 1011 m. Find the radius of the image of the sun formed by a lens of focal length 20 cm.
Explain: ‘How is a rainbow formed’?
Answer the following question in detail.
Explain the formation of a secondary rainbow. For which angular range with the horizontal is it visible?
Answer the following question in detail.
Is it possible to see primary and secondary rainbow simultaneously? Under what conditions?
Pick the wrong answer in the context with rainbow.
State any one difference between a primary rainbow and a secondary rainbow.
A parallel beam of light of wavelength 5890 Å falls normally on a slit of width 0.2 mm. Find the distance between the first minima on the two sides of the central maximum of the diffraction pattern observed on a screen placed in the focal plane of a convex lens of focal length 50 cm. The lens is placed quite close to the slit.
| 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 : |
In an optical fibre, if n1 and n2 are the refractive indices of the core and cladding, then which among the following, would be a correct equation?
| 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 diamond is immersed in such a liquid which has its refractive index with respect to air as greater than the refractive index of water with respect to air. Then the critical angle of diamond-liquid interface as compared to critical angle of diamond-water interface will
The sky would appear red instead of blue if
A passenger in an aeroplane shall ______.
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°.
