MEDIUM
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Parallel rays of light are falling on convex spherical surface of radius of curvature R=20 cm as shown. Refractive index of the medium is μ=1.5. After refraction from the spherical surface parallel rays

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Important Questions on Ray Optics and Optical Instruments

HARD

For refraction at a convex spherical surface of radius of curvatureR from a medium of refractive index n1 to medium of refractive index n2(n2>n1), establish the relation:

nv-nu=n2-n1R.

 What will be behaver of a convex lens of the refractive index 1.47 when it is immersed in a liquid of refractive index 1.47?

MEDIUM
The power of a biconvex lens is 10 dioptre and the radius of curvature of each surface is 10 cm. Then the refractive index of the material of the lens is,
MEDIUM
A concave glass lens of refractive index 1.5 is immersed in carbon di-sulfide (refractive index =1.6). Which of the following is true?
[ Assume both surfaces of the lens have same radius of curvature =R]
EASY
In a Galilean telescope, the eye lens is one convex lens and one _____ lens.
MEDIUM
Diameter of a plano - convex lens is 6 cm and thickness at the centre is 3 mm. If the speed of light in the material of lens is 2×108 m s-1, the focal length of the lens is:
HARD
With the help of a ray diagram, show the formation of the image of a point object by the refraction of light at a spherical convex surface separating two media of refraction indices μ1 and μ2 (μ2>μ1) respectively, Using this diagram derive the relation:μ2v-μ1u=μ2-μ1R

Where used symbols have their usual meanings
EASY
There is a small air bubble at the centre of a solid glass sphere of radius r and refractive index μ. What will be the apparent distance of the bubble from the centre of the sphere, when viewed from outside?
HARD
Deduce the relation between n, u,v, R for refraction at a spherical surface, where the symbols have their usual meaning.
MEDIUM

A light ray enters a solid glass sphere of refractive index μ=3 at an angle of incidence 60°. The ray is both reflected and refracted at the farther surface of the sphere. The angle (in degrees) between the reflected and refracted rays at this surface is:

MEDIUM

A parallel beam of light strikes a piece of transparent glass having cross section as shown in the figure below. Correct shape of the emergent wavefront will be (figures are schematic and not drawn to scale)

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EASY

A magician during a show makes a glass lens with n =1.47 disappear in a trough of liquid.

Could the liquid be water?

MEDIUM
Two identical glass rods S1 and S2 (refractive index = 1.5) have one convex end of radius of curvature 10 cm. They are placed with the curved surfaces at a distance d as shown in the figure, with their axes (shown by the dashed line) aligned. When a point source of light P is placed inside rod S1 on its axis at a distance of 50 cm from the curved face, the light rays emanating from it are found to be parallel to the axis inside S2 . The distance d is

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MEDIUM
Derive the formula for the focal length of a thin lens with the help of refraction formula of spherical surface.
HARD

Derive an expression for refraction at a single(convex) spherical surface, i.e. a relation between u, v, R, n1(rarer medium) and n2(denser medium), where the terms have their usual meaning.

MEDIUM
Derive the formula for the refraction at a convex spherical surface.
EASY
Two transparent media having refractive indices 1.0 and 1.5 are separated by a spherical refracting surface of radius of curvature 30 cm. The centre of curvature of surface is towards denser medium and a point object is placed on the principal axis in rarer medium at a distance of 15 cm from the pole of the surface. The distance of image from the pole of the surface is cm.
MEDIUM
A parallel beam of light is allowed to fall on a transparent spherical globe of diameter 30 cm and refractive index 1.5. The distance from the centre of the globe at which beam of light can converge is _____ mm.
HARD

A beaker of radius r is filled with waterrefractive index 43 up to a height H as shown in the figure on the left. The beaker is kept on a horizontal table rotating with angular speed ω. This makes the water surface curved so that the difference in the height of water level at the centre and at the circumference of the beaker is hhH, hr, as shown in the figure on the right. Take this surface to be approximately spherical with a radius of curvature R. Which of the following is/are correct? (g is the acceleration due to gravity)

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HARD

A transparent thin film of uniform thickness and refractive index n1=1.4 is coated on the convex spherical surface of radius R at one end of a long solid glass cylinder of refractive index n2=1.5 , as shown in the figure. Rays of light parallel to the axis of the cylinder traversing through the film from air to glass get focused at distance f1 from the film, while rays of light traversing from glass to air get focused at distance f2 from the film. Then

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HARD
The eye can be regarded as a single refracting surface. The radius of curvature of this surface is equal to that of the cornea (7.8 mm). This surface separates two media of refractive indices 1 and 1.34. Calculate the distance from the refracting surface at which a parallel beam of light will come to focus.