Explanation:
The capacitance of a parallel plate capacitor is directly proportional to the area of the plates and permittivity of the medium between the plates. It is indirectly proportional to the distance between the plates.
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The Bohr radius of the fifth electron of phosphorus (atomic number = 15) acting as dopant in silicon (relative dielectric constant = 12) is
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(a) 10.6 Å |
(b) 0.53 Å |
(c) 21.2 Å |
(d) None of these |
A planet which is born sister of earth is
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(a) Mercury |
(b) Venus |
(c) Mars |
(d) Jupiter |
It is desired to photograph the image of an object placed at a distance of 3m from the plane mirror. The camera which is at a distance of 4.5 m from the mirror should be focussed for a distance of
| (a) 3m | (b) 4.5m | (c) 6m | (d) 7.5 m |
Assertion : Newton’s rings are formed in the reflected system. When the space between the lens and the glass plate is filled with a liquid of refractive index greater than that of glass, the central spot of the pattern is dark.
Reason : The reflection is Newton’s ring cases will be from a denser to a rarer medium and the two interfering rays are reflected under similar conditions.
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(a) If both assertion and reason are true and the reason is the correct explanation of the assertion. |
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(b) If both assertion and reason are true but reason is not the correct explanation of the assertion. |
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(c) If assertion is true but reason is false. |
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(d) If the assertion and reason both are false. |
Assertion : Neutrons penetrate matter more readily as compared to protons.
Reason : Neutrons are slightly more massive than protons.
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(a) If both assertion and reason are true and the reason is the correct explanation of the assertion. |
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(b) If both assertion and reason are true but reason is not the correct explanation of the assertion. |
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(c) If assertion is true but reason is false. |
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(d) If the assertion and reason both are false. |
An electron in the n = 1 orbit of hydrogen atom is bound by 13.6 eV. If a hydrogen atom is in the n = 3 state, how much energy is required to ionize it
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(a) 13.6 eV |
(b) 4.53 eV |
(c) 3.4 eV |
(d) 1.51 eV |
Coating of strontium oxide on Tungsten cathode in a valve is good for thermionic emission because
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(a) Work function decreases |
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(b) Work function increases |
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(c) Conductivity of cathode increases |
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(d) Cathode can be heated to high temperature |
Two circuits have coefficient of mutual induction of 0.09 henry. Average e.m.f. induced in the secondary by a change of current from 0 to 20 ampere in 0.006 second in the primary will be
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(a) 120 V |
(b) 80 V |
(c) 200 V |
(d) 300 V |