In an interference experiment, third bright fringe is obtained at a point on the screen with a light of 700 nm. What should be the wavelength of the light source in order to obtain 5th bright fringe at the same point
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(a) 500 nm |
(b) 630 nm |
(c) 750 nm |
(d) 420 nm |
(d) 420 nm
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The electric resistance of a certain wire of iron is R. If its length and radius are both doubled, then
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(a) The resistance will be doubled and the specific resistance will be halved |
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(b) The resistance will be halved and the specific resistance will remain unchanged |
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(c) The resistance will be halved and the specific resistance will be doubled |
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(d) The resistance and the specific resistance, will both remain unchanged |
A circular loop of area 
carrying a current of 10 A, is held perpendicular to a magnetic field of intensity 0.1T. The torque acting on the loop is
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(a) Zero |
(b) 0.01 N-m |
(c) 0.001 N-m |
(d) 0.8 N-m |
A charge q is placed at the centre of the line joining two equal charges Q. The system of the three charges will be in equilibrium, if q is equal to
(a) 
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(b) 
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(b)
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(d) 
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