EASY
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The image is always inverted.

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Important Questions on Light

EASY
A convex lens shown in the figure is made up of two types of transparent materials. A point sources of light is placed on its principal axis. If reflections from the boundaries between layers are ignored, the lens will form
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EASY
An object is placed at a distance 24 cm in front of a convex lens of focal length 8 cm. What is the nature of the image so formed?
HARD

A virtual, diminished image is formed when an object is placed between the optical centre and the principal focus of a lens.
(i) Name the type of lens which forms the above image.
(ii) Draw a ray diagram to show the formation of the image with the above stated characteristics.  

EASY
If the image formed by a thin convex lens of power P has magnification m then image distance v is
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
HARD

Four bulbs; red, green, white and blue (denoted by R, G, W and B respectively) are kept in front of a converging lens (as shown in the figure below). The observer sees that the green and blue bulbs are kept to the left of the principle axis while the red and white bulbs are kept to the right of the principle axis. He also sees that the red and green bulbs are above the principle axis while the white and blue bulbs are below the principle axis. The screens S1 and S2 are set at appropriate positions for the focusing to view the images.

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Choose the figure that correctly represents the images as seen by the observer.

HARD

An object is placed at a distance 24 cm in front of a convex lens of focal length 8 cm.
(i) Calculate the distance of the image from the lens.
(ii) Calculate the magnification of the image.

EASY

When a drop of water is introduced between the glass plate and plano convex lens in Newton's rings system, the ring system:

MEDIUM
A concave lens has focal length 15 cm. At what distance should the object from the lens be placed so that it forms an image at 10 cm from the lens? Also find the magnification produced by the lens.
EASY
Which lens, thick or thin has greater focal length?
EASY
A point source of light is placed at 2 f from a converging lens of focal length f. A flat mirror is placed on the other side of the lens at a distance d such that rays reflected from the mirror are parallel after passing through the lens again. If f=30 cm, then d is equal to
 
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?
EASY
State the position of the object in front of a converging lens if It produces a real and same size image of the object.
MEDIUM
A planoconvex lens has thickness of 4 cm. When placed on a horizontal table, with the curved surface in contact with it, the apparent depth of the bottom most point of the lens is found to be 3 cm. If the lens is inverted such that the plane face is in contact with the table, the apparent depth of the centre of the plane face is found to be 258 cm. The focal length of the lens is (assume thickness of lens to be negligible)
EASY
State the position of the object in front of a converging lens if It is used as a magnifying lens.
HARD

An object AB is placed between O and F1 on the principal axis of a converging lens as shown in the diagram.

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Copy the diagram and by using three standard rays starting from point A, obtain an image of the object AB.

EASY
Where should an object be placed in front of a convex lens to get a real image of the size of the object? 
EASY
If the lens is placed in water instead of air, how does its focal length change? 
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?

 

 

HARD
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