When light rays from the sun fall on a convex lens along a direction parallel to its axis
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(a) Focal length for all colours is the same |
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(b) Focal length for violet colour is the shortest |
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(c) Focal length for yellow colour is the longest |
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(d) Focal length for red colour is the shortest |
(b) Focal length for violet colour is the shortest
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A white screen illuminated by green and red light appears to be
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(a) Green |
(b) Red |
(c) Yellow |
(d) White |
The graph which represents the correct variation of logarithm of activity (log A) versus time, in figure is
|
(a) A |
(b) B |
(c) C |
(d) D |
When the temperature of silicon sample is increased from 27℃ to 100℃, the conductivity of silicon will be
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(a) Increased |
(b) Decreased |
(c) Remain same |
(d) Zero |
The ammeter A reads 2 A and the voltmeter V reads 20 V. the value of resistance R is (Assuming finite resistance's of ammeter and voltmeter)
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(a) Exactly 10 ohm |
(b) Less than 10 ohm |
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(c) More than 10 ohm |
(d) We cannot definitely say |
A virtual image larger than the object can be obtained by
|
(a) Concave mirror |
(b) Convex mirror |
(c) Plane mirror |
(d) Concave lens |
Light appears to travel in straight lines since
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(a) It is not absorbed by the atmosphere |
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(b) It is reflected by the atmosphere |
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(c) Its wavelength is very small |
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(d) Its velocity is very large |
The electric field E, current density J and conductivity s of a conductor are related as
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(a) σ = E/j |
(b) σ = j/E |
(c) σ = jE |
(d) σ = 1/jE |