MCQ
1 micro farad =
- A10-7
- B10-6
- C10-5
- D10-9
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A silver ball of radius 4.8 cm is suspended by a thread in the vacuum chamber. UV light of wavelength 200 nm is incident on the ball for some times during which a total energy of 1 × 10–7 J falls on the surface. Assuming on an average one out of 103 photons incident is able to eject electron. The potential on sphere will be
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(a) 1 V |
(b) 2 V |
(c) 3 V |
(d) Zero |
Assertion : X-rays can penetrate through the flesh but not through the bones.
Reason : The penetrating power of X-rays depends on voltage.
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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. |
A house is served by 220 V supply line in a circuit protected by a 9 ampere fuse. The maximum number of 60 W lamps in parallel that can be turned on, is
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(a) 44 |
(b) 20 |
(c) 22 |
(d) 33 |
Ray optics fails when
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(a) The size of the obstacle is 5 cm |
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(b) The size of the obstacle is 3 cm |
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(c) The size of the obstacle is less than the wavelength of light |
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(d) (a) and (b) both |
A magnetic field
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(a) Always exerts a force on a charged particle |
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(b) Never exerts a force on a charged particle |
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(c) Exerts a force, if the charged particle is moving across the magnetic field lines |
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(d) Exerts a force, if the charged particle is moving along the magnetic field lines |