Physics

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(d) The speed of the image of the car would appear to increase as the distance between the cars decreases.

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Here, light ray goes from (optically) rarer medium air to optically denser terpentine, then it bends towards the normal i.e., i>r whereas when it goes from to optically denser medium terpentine to rarer medium water. then it bends away the normal i.e., i

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(b) The PQ ray of light passes through focus F and incident on the concave mirror, after reflection, should become parallel to the principal axis and shown by ray-2 in the figure.

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(b) The phenomenon involved in the reflection of radio waves by ionosphere is similar to total internal reflection of light in air during a mirage i.e., angle of incidence is greater than critical angle.

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(c) R= 20cm, $\mu$ = 1.5, f= $\frac{R}{\mu -1}$ = $\frac{20}{1.5-1}$ =40cm so lens acts as convex lens.

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(c) According to VIBGYOR, among all given sources of light, the blue light have the smallest wavelength. According to Cauchy relationship, smaller the wavelength higher the refractive index and consequently smaller the critical angle. So, corresponding to blue colour, the critical angle is least which facilitates total internal reflection for the beam of blue light. The beam of green light would also undergo total internal reflection.

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(b) A passenger in an aeroplane may see a primary and a secondary rainbow like concentric circles.

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(c) When an object approaches a convergent lens from the left of the lens with a uniform speed of 5 m/s, the image away from the lens with a non-uniform acceleration.

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(d) Since v ∝ λ, the light of red colour is of the highest wavelength and therefore of the highest speed. Therefore, after travelling through the slab, the red colour emerge first.

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(a) since deviation  $\delta =(\mu -1)A$ = (1.5-1)5⁰= 2.5⁰

But $\delta =\theta -r$ so$\theta =\mathrm{7.5\; °}$