EASY

Earn 100

Explain paraxial approximation.

Important Questions on Refraction of Light at Curved Surface

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A beam of light converges at a point

P

. Now a lens is placed in the path of the convergent beam

12 cm

from

P

. At what point does the beam converge if the lens is a concave lens of focal length

16 cm

EASY

Science>Physics>Refraction of Light at Curved Surface>Refraction of Light at Curved Surface

A convex lens is dipped in a liquid whose refractive index is equal to the refractive index of the lens. Then, it's focal length will:

HARD

Science>Physics>Refraction of Light at Curved Surface>Refraction of Light at Curved Surface

Figure below shows an equiconvex lens (of refractive index

1.50

) in contact with a liquid layer on top of a plane mirror. A small needle with its tip on the principal axis is moved along the axis until its inverted image is found at the position of the needle. The distance of the needle from the lens is measured to be

45.0 c m

. The liquid is removed and the experiment is repeated. The new distance is measured to be

30.0 c m

. What is the refractive index of the liquid?
Question Image

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Science>Physics>Refraction of Light at Curved Surface>Refraction of Light at Curved Surface

Radii of curvature of a converging lens are in the ratio

1 : 2

. Its focal length is

6 c m

and refractive index is

1.5

. Then its radii of curvature are:

HARD

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A convex lens of focal length

0.2 c m

and made of glass

(^{a} μ_{w} = 1.5)

is immersed in water

(^{a} μ_{w} = 1.33)

. Find the change in the focal length of the lens.

MEDIUM

Science>Physics>Refraction of Light at Curved Surface>Refraction of Light at Curved Surface

A person with normal near point

25 c m

uses a compound microscope with an objective of focal length

8.0 m m

and an eyepiece of focal length

2.5 c m

to bring an object placed at

9.0 m m

from the objective in sharp focus. The separation between two lenses and magnification respectively are

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Science>Physics>Refraction of Light at Curved Surface>Refraction of Light at Curved Surface

There is a convex lens of focal length

30 cm

and a concave lens of focal length

20 cm

and distance between both the lenses is

8 cm

. An object

1.5 c m

in size is placed on the side of the convex lens. The distance between the object and the convex lens is

40 c m

. Determine the magnification produced by the two-lens system, and the size of the image.

MEDIUM

Science>Physics>Refraction of Light at Curved Surface>Refraction of Light at Curved Surface

The image of a small electric bulb fixed on the wall of a room is to be obtained on the opposite wall

3 m

away by means of a large convex lens. What is the maximum possible focal length of the lens required for the purpose?

MEDIUM

Science>Physics>Refraction of Light at Curved Surface>Refraction of Light at Curved Surface

The refractive index of material of a Plano-convex lens, if the radius of curvature of the plane surface

(R_{1})

is infinite while the radius of curvature of convex surface

(R_{2})

20 c m

and focal length of the lens is

30 c m

, will be:

EASY

Science>Physics>Refraction of Light at Curved Surface>Refraction of Light at Curved Surface

A plano-convex lens has refractive index

μ_{1}

and focal length

f_{1}

and another plano-concave lens has refractive index

μ_{2}

and focal length

f_{2}

. Radius of curvature in both lenses is same. If

f_{1} = 2 f_{2}

then relation between

μ_{1}

and

μ_{2}

MEDIUM

Science>Physics>Refraction of Light at Curved Surface>Refraction of Light at Curved Surface

A man is trying to start a fire by focusing sunlight on a piece of paper using an equi-convex lens of focal length

10 c m

. The diameter of the sun is

1.39 \times 10^{9} m

and its mean distance from the earth is

1.5 \times 10^{11} m

. The diameter of the sun's image on the paper is (close to)

MEDIUM

Science>Physics>Refraction of Light at Curved Surface>Refraction of Light at Curved Surface

Light from a point source in air falls on a convex spherical glass surface whose radius of curvature and refractive index are

20 c m

and

1.5

respectively. If the distance of light source from the glass surface is

100 c m

, then the position of image will be formed at:

EASY

Science>Physics>Refraction of Light at Curved Surface>Refraction of Light at Curved Surface

The radius of curvature of each surface of a convex lens of refractive index

1.5

40 c m

. Calculate the power of this lens.

EASY

Science>Physics>Refraction of Light at Curved Surface>Refraction of Light at Curved Surface

An object is placed at a distance of

1.5 m

from the screen and a convex lens is interposed between them. The magnification produced is

4

. What is the focal length of the lens.

MEDIUM

Science>Physics>Refraction of Light at Curved Surface>Refraction of Light at Curved Surface

Determine the ‘effective focal length’ of the combination of the two lenses, concave and convex, if they are placed $8.0 c m$ apart with their principal axes coincident. Does the answer depend on which side of the combination a beam of parallel light is incident? Is the notion of effective focal length of this system useful at all? The focal length of the concave lens $= 30 cm$ and the focal length of the convex lens $= - 20 cm$ .

HARD

Science>Physics>Refraction of Light at Curved Surface>Refraction of Light at Curved Surface

From a point source, light falls on a spherical glass surface

(μ = 1.5

and radius of curvature

= 10 c m)

. The distance between point source and glass surface is

50 c m

. The position of the image is

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Science>Physics>Refraction of Light at Curved Surface>Refraction of Light at Curved Surface

A card sheet divided into squares each of size $1 m m^{2}$ is being viewed through a magnifying glass (a converging lens of focal length $10 cm$ ) held close to the eye. What should be the distance between the object in and the magnifying glass if the virtual image of each square in the figure is to have an area of $6.25 m m^{2}$ . Would you be able to see the squares distinctly with your eyes very close to the magnifier?

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Science>Physics>Refraction of Light at Curved Surface>Refraction of Light at Curved Surface

A screen is placed

90 c m

from an object. The image of the object on the screen is formed by a convex lens placed at two different locations separated by

20 c m

. Determine the focal length of the lens.

HARD

Science>Physics>Refraction of Light at Curved Surface>Refraction of Light at Curved Surface

Two thin symmetrical lens of different nature have equal radii of curvature of all faces R = 20 cm. The lenses are put close together and immersed in water. The focal length of the system is 24 cm. The difference between refractive indices of the two lenses is ……

\times \frac{1}{9}

Refractive index of water is

\frac{4}{3}

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Science>Physics>Refraction of Light at Curved Surface>Refraction of Light at Curved Surface

A square card of side length

1 m m

is being seen through a magnifying lens of focal length

10 c m

. The card is placed at a distance of

9 c m

from the lens. The apparent area of the card through the lens is:

Explain paraxial approximation.

Important Questions on Refraction of Light at Curved Surface

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