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A plastic hemisphere has a radius of curvature of 8 cm and an index of refraction of 1.2. On the axis half way between the plane surface and the spherical one (4 cm from each) is a small object O. The distance between two images when viewed along the axis from the two sides of the hemisphere is approximately in cm.

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Important Questions on Ray Optics and Optical Instruments

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Physics>Optics>Ray Optics and Optical Instruments>Refraction at Spherical Surfaces and by Lenses

A small object is placed $50 cm$ to the left of thin convex lens of focal length $30 cm$ . A convex spherical mirror of radius of curvature $100 cm$ is placed to the right of the lens at a distance of $50 cm$ . The mirror is tilted such that the axis of the mirror is at an angle $θ = 30 °$ to the axis of the lens, as shown in the figure. If the origin of the coordinate system is taken to be at the centre of the lens, the coordinates (in $cm$ ) of the point $(x, y)$ at which the image is formed are:

MEDIUM

Physics>Optics>Ray Optics and Optical Instruments>Refraction at Spherical Surfaces and by Lenses

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

Physics>Optics>Ray Optics and Optical Instruments>Refraction at Spherical Surfaces and by Lenses

A convex lens is put

10 c m

from a light source and it makes a sharp image on a screen, kept

10 c m

from the lens. Now a glass block (refractive index 1.5) of

1.5 c m

thickness is placed in between the light source and the lens. To get the sharp image again, the screen is shifted by a distance

d .

Then

d

is:

MEDIUM

Physics>Optics>Ray Optics and Optical Instruments>Refraction at Spherical Surfaces and by Lenses

A plano - convex lens (focal length

f_{2}

, refractive index

μ_{2},

radius of curvature R) fits exactly into a plano - concave lens (focal length

f_{1},

refractive index

μ_{1},

radius of curvature R). Their plane surfaces are parallel to each other. Then, the focal length of the combination will be:

HARD

Physics>Optics>Ray Optics and Optical Instruments>Refraction at Spherical Surfaces and by Lenses

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.

EASY

Physics>Optics>Ray Optics and Optical Instruments>Refraction at Spherical Surfaces and by Lenses

Formation of real image using a biconvex lens is shown below:

If the whole set up is immersed in water without disturbing the object and the screen positions, what will one observe on the screen?

EASY

Physics>Optics>Ray Optics and Optical Instruments>Refraction at Spherical Surfaces and by Lenses

For a thin lens of focal length

f

, if the object and image distances from the optical centre are

u

and

v

, then which of the following is the correct lens formula? (Assume standard sign-convention)

MEDIUM

Physics>Optics>Ray Optics and Optical Instruments>Refraction at Spherical Surfaces and by Lenses

Two identical glass

(μ_{g} = \frac{3}{2})

equiconvex lenses of focal length,

f

are kept in contact. The space between the two lenses is filled with water

(μ_{w} = \frac{4}{3})

. The focal length of the combination is

EASY

Physics>Optics>Ray Optics and Optical Instruments>Refraction at Spherical Surfaces and by Lenses

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?

MEDIUM

Physics>Optics>Ray Optics and Optical Instruments>Refraction at Spherical Surfaces and by Lenses

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

]

HARD

Physics>Optics>Ray Optics and Optical Instruments>Refraction at Spherical Surfaces and by Lenses

What is the position and nature of image formed by lens combination shown in figure? (

f_{1}, f_{2}

are focal lengths)

MEDIUM

Physics>Optics>Ray Optics and Optical Instruments>Refraction at Spherical Surfaces and by Lenses

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)

MEDIUM

Physics>Optics>Ray Optics and Optical Instruments>Refraction at Spherical Surfaces and by Lenses

A convex lens of focal length

f

is placed some where in between an object and a screen. The distance between object and screen is

x

. If numerical value of magnification produced by lens is

m

, focal length of lens is

EASY

Physics>Optics>Ray Optics and Optical Instruments>Refraction at Spherical Surfaces and by Lenses

A plano-convex lens of refractive index

μ_{1}

and focal length

f_{1}

is kept in contact with another plano-concave lens of refractive index

μ_{2}

and focal length

f_{2} .

If the radius of curvature of their spherical faces is

R

each and

f_{1} = 2 f_{2},

the

μ_{1}

and

μ_{2}

are related as:

MEDIUM

Physics>Optics>Ray Optics and Optical Instruments>Refraction at Spherical Surfaces and by Lenses

Two thin lenses have a combined power of

+ 9 D .

When they are separated by a distance of

20 cm,

their equivalent power becomes

+ \frac{27}{5} D,

then their individual powers are

HARD

Physics>Optics>Ray Optics and Optical Instruments>Refraction at Spherical Surfaces and by Lenses

A point source of light is moving at a rate of

2 cm s^{- 1}

towards a thin convex lens of focal length

10 cm

along its optical axis. When the source is

15 cm

away from the lens the image is moving at

HARD

Physics>Optics>Ray Optics and Optical Instruments>Refraction at Spherical Surfaces and by Lenses

A diverging lens with magnitude of focal length

25 cm

is placed at a distance of

15 cm

from a converging lens of magnitude of focal length

20 cm

. A beam of parallel light falls on the diverging lens. The final image formed is:

MEDIUM

Physics>Optics>Ray Optics and Optical Instruments>Refraction at Spherical Surfaces and by Lenses

A light ray enters a solid glass sphere of refractive index $μ = \sqrt{3}$ 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

Physics>Optics>Ray Optics and Optical Instruments>Refraction at Spherical Surfaces and by Lenses

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

Physics>Optics>Ray Optics and Optical Instruments>Refraction at Spherical Surfaces and by Lenses

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 \times 1 0^{8} m s^{- 1}

, the focal length of the lens is:

Important Questions on Ray Optics and Optical Instruments

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