In a Young's double slit experiment, the fringe width will remain same, if (D = distance between screen and plane of slits, d = separation between two slits and λ = wavelength of light used)
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(a) Both λ and D are doubled |
(b) Both d and D are doubled |
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(c) D is doubled but d is halved |
(d) λ is doubled but d is halved |
(b) Both d and D are doubled
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A manufacturer uses a concave lens instead of a convex lens in a magnifying glass by mistake. What will be the effect on the working of the lens?
Correct exposure for a photographic print is 10 seconds at a distance of one metre from a point source of 20 candela. For an equal fogging of the print placed at a distance of 2 m from a 16 candela source, the necessary time for exposure is
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(a) 100 sec |
(b) 25 sec |
(c) 50 sec |
(d) 75 sec |
The work function of a metal is
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(a) The energy for the electron to enter into the metal |
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(b) The energy for producing X-ray |
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(c) The energy for the electron to come out from metal surface |
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(d) None of these |
In case of NPN-transistors the collector current is always less than the emitter current because
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(a) Collector side is reverse biased and emitter side is forward biased |
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(b) After electrons are lost in the base and only remaining ones reach the collector |
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(c) Collector side is forward biased and emitter side is reverse biased |
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(d) Collector being reverse biased attracts less electrons |
Which of the following is most unstable
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(a) Electrons |
(b) Protons |
(c) Neutrons |
(d) α -particle |
What is the equivalent resistance between A and B in the figure below if R = 3Ω
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(a) 9 Ω |
(b) 12 Ω |
(c) 15 Ω |
(d) None of these |
Carbon dating is best suited for determining the age of fossils if their age in years is of the order of
(a) 
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(b) 
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(c) 
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(d) 
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