Explanation:
Doppler effect refers to the change in wave frequency during the relative motion between a wave source and it's observer by considering that the Velocity of the observer with respect to the source velocity is negligible.
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Assertion : Penetrating power of X-rays increases with the increasing the wavelength.
Reason : The penetrating power of X-rays increases with the frequency of X-rays.
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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 assertion is false but reason is true. |
Light of wavelength 
strikes a photo-sensitive surface and electrons are ejected with kinetic energy E. If the kinetic energy is to be increased to 2E, the wavelength must be changed to 
where
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(a) |
(b) |
(c) |
(d) |
A capacitor of 10mF charged up to 250 volts is connected in parallel with another capacitor of 5mF charged up to 100 volts. The common potential is
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(a) 500 V |
(b) 400 V |
(c) 300 V |
(d) 200 V |
The magnetic needle of a tangent galvanometer is deflected at an angle 30o due to a magnet. The horizontal component of earth’s magnetic field 0.34 × 10–4 T is along the plane of the coil. The magnetic intensity is
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(a) 1.96 × 10–4 T |
(b) 1.96 × 10–5 T |
(c) 1.96 × 104 T |
(d) 1.96 × 105 T |
A semiconductor is cooled from 
to 
Its resistance
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(a) Will decrease |
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(b) Will increase |
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(c) Will first decrease and then increase |
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(d) Will not change |
The difference in the lengths of a mean solar day and a sidereal day is about
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(a) 1 min |
(b) 4 min |
(c) 15 min |
(d) 56 min |
The example for non-ohmic resistance is
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(a) Copper wire |
(b) Carbon resistance |
(c) Diode |
(d) Tungston wire |
