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An object gets closer to the focal point of a convex lens from infinity, its image

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Important Questions on Eye and Optical Instruments

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Physics>Optics>Eye and Optical Instruments>Simple Microscope
With a neat labelled diagram explain the formation of image in a simple microscope.
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Physics>Optics>Eye and Optical Instruments>Simple Microscope
Two identical thin Plano-convex glass lenses (refractive index 1.5 ) each having radius of curvature of 20 cm are placed with their convex surfaces in contact at the center. The intervening space is filled with oil of refractive index 1.7 The focal length of the combination is
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Physics>Optics>Eye and Optical Instruments>Simple Microscope
What is the magnifying power of a simple microscope of focal length 5 cm, if the image is formed at the distance of distinct vision?
MEDIUM
Physics>Optics>Eye and Optical Instruments>Simple Microscope
In a compound microscope, the magnified virtual image is formed at a distance of 25 cm from the eye-piece. The focal length of its objective lens is 1 cm. If the magnification is 100 and the tube length of the microscope is 20 cm, then the focal length of the eye-piece lens (in cm) is ______
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Physics>Optics>Eye and Optical Instruments>Simple Microscope
To determine refractive index of glass slab using a travelling microscope, minimum number of readings required are :
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Physics>Optics>Eye and Optical Instruments>Simple Microscope
A convex lens of focal length 12.5 cm is used as a simple microscope. When the image is formed at infinite, Magnification is ______ (Near point for the normal vision is 25 cm).
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Physics>Optics>Eye and Optical Instruments>Simple Microscope
A combination of two thin convex lenses of focal length 0.3 m and 0.1 m will have minimum spherical and chromatic aberrations if the distance between them is
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Physics>Optics>Eye and Optical Instruments>Simple Microscope
Microscope is an optical instrument which
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Physics>Optics>Eye and Optical Instruments>Simple Microscope
A microscope is focussed on a mark in a piece of paper and then a slab of thickness 3 cm and refractive index 32 is placed over the mark. How should the microscope be moved to get the mark in focus again?
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Physics>Optics>Eye and Optical Instruments>Simple Microscope
With a simple microscope,if the final image is located at the least distance of distinct vision, (i.e. D ) from the eye placed close to the lens, then the magnifying power is
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Physics>Optics>Eye and Optical Instruments>Simple Microscope
A travelling microscope gives the view of meniscus as -
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Physics>Optics>Eye and Optical Instruments>Simple Microscope
Magnification at least distance of distinct vision of a simple microscope having its focal length 5 cm is
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Physics>Optics>Eye and Optical Instruments>Simple Microscope
A bi-convex lens is formed with two thin plano-convex lenses as shown in the figure. Refractive index n of the first lens is 1.5 and that of the second lens is 1.2. Both the curved surfaces are of the same radius of curvature R=14 cm. for this bi-convex lens, for an object distance of 40 cm, the image distance will be
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MEDIUM
Physics>Optics>Eye and Optical Instruments>Simple Microscope
A convex lens A of focal length 20 cm and a concave lens B of focal length 5 cm are kept along the same axis with a distance d between them. If a parallel beam of light falling on A leaves B as a parallel beam, then d is equal to _________ cm.
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Physics>Optics>Eye and Optical Instruments>Simple Microscope
How should people wearing their spectacles work with a microscope
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Physics>Optics>Eye and Optical Instruments>Simple Microscope
An electron microscope is superior to an optical microscope in
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Physics>Optics>Eye and Optical Instruments>Simple Microscope
A travelling microscope gives the view of meniscus as -
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Physics>Optics>Eye and Optical Instruments>Simple Microscope
Dispersive powers of materials used in lenses of an achromatic doublet are in the ratio 5:3. If the focal length of the concave lens is 15 cm, then the focal length of the other lens will be
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Physics>Optics>Eye and Optical Instruments>Simple Microscope
The plane faces of two identical plano-convex lenses each having a focal length of 50 cm are placed against each other to form a usual biconvex lens. The distance from this lens combination at which an object must be placed to obtain a real, inverted image which has the same size as the object is
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Physics>Optics>Eye and Optical Instruments>Simple Microscope
A telescope consists of two thin lenses of focal lengths 0.3 m and 3 cm respectively. It is focused on moon which subtends on angle of 0.5° at the objective. Then, the angle subtended at the eye by the final image will be