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An object O is placed at a distance of 20 cm from a thin Plano-convex lens of focal length 15 cm. The plane surface of the lens is silvered as shown in Fig. The image is formed at a distance of

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Important Questions on Ray Optics

HARD
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:
HARD
A thin convex lens of focal length f is put on a plane mirror as shown in the figure. When an object is kept at a distance a from the lens-mirror combination, its image is formed at a distance a3 in front of the combination. The value of a is:
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MEDIUM
Two identical glass μg=32 equiconvex lenses of focal length, f are kept in contact. The space between the two lenses is filled with water μw=43. The focal length of the combination is
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A concave lens made of material of refractive index 1.6 is immersed in a medium of refractive index 2.0. The two surfaces of the concave lens have the same radius of curvature 0.2 m. The lens will behave as a
HARD
What is the position and nature of image formed by lens combination shown in figure? ( f1, f2 are focal lengths)

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MEDIUM
An optical device is constructed by fixing three identical convex lenses of focal lengths 10 cm each inside a hollow tube at an equal spacing of 30 cm each. One end of the device is placed 10 cm away from a point source. How much does the image shift when the device is moved away from the source by another 10 cm?
MEDIUM
Two thin lenses have a combined power of +9 D. When they are separated by a distance of 20 cm, their equivalent power becomes +275 D, then their individual powers are
MEDIUM
A hollow lens is made of thin glass and in the shape of a double concave lens. It can be filled with air, water of refractive index 1.33 or CS2 of refractive index 1.6. It will act a diverging lens if it is
EASY
A plano-convex lens of refractive index μ1 and focal length f1 is kept in contact with another plano-concave lens of refractive index μ2 and focal length f2. If the radius of curvature of their spherical faces is R each and f1=2f2, the μ1 and μ2 are related as:
HARD
Sunlight of intensity 1.3 kW m-2 is incident normally on a thin convex lens of focal length 20 cm. Ignore the energy loss of light due to the lens and assume that the lens aperture size is much smaller than its focal length. The average intensity of light, in kW m-2 , at a distance 22 cm from the lens on the other side is __________.
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The image of an object, formed by a plano - convex lens at a distance of 8 m behind the lens, is real and is one-third the size of the object. The wavelength of light inside the lens is   2 3  times the wavelength in free space. The radius of the curved surface of the lens is
EASY
Formation of real image using a biconvex lens is shown below:

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

The word KVPY is written on a board and viewed through different lenses such that board is at a distance beyond the focal length of the lens.

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Ignoring magnification effects, consider the following statements.
(I) First image has been viewed from the planar side of a plano-concave lens and second image from the planar side of a plano-convex lens.
(II) First image has been viewed from the concave side of a plano-concave lens and second image from the convex side of a plano-convex lens.
(III) First image has been viewed from the concave side of a plano-concave lens and second image from the planar side of a plano-convex lens.
(IV) First image has been viewed from the planar side of a plano-concave lens and second image from the convex side of a plano-convexlens.

Which of the above statements are correct?

 

 

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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
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A point object is placed 20 cm left of a convex lens of focal length, f=5 cm (see the figure). The lens is made to oscillate with a small amplitude A along the horizontal axis. The image of the object will also oscillate along the axis with
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MEDIUM
The flat face of a plano-convex lens of focel length 10 cm is silvered. A point source placed 30 cm in front of the curved surface will produce a:
MEDIUM
In an experiment a convex lens of focal length 15 cm is placed coaxially on an optical bench in front of a convex mirror at a distance of 5 cm from it. It is found that an object and its image coincide, if the object is placed at a distance of 20 cm from the lens. The focal length of the convex mirror is-
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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
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A plano - convex lens (focal length f2 , refractive index μ2, radius of curvature R) fits exactly into a plano - concave lens (focal length f1, refractive index μ1, radius of curvature R). Their plane surfaces are parallel to each other. Then, the focal length of the combination will be:
HARD

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:

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