Explanation:
Polarization is a property of waves that can oscillate with more than one orientation. Electromagnetic waves such as light exhibit polarization, as do some other types of wave, such as gravitational waves.
Sound waves in a gas or liquid do not exhibit polarization, since the oscillation is always in the direction the wave travels.
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A concave lens of focal length 20 cm placed in contact with a plane mirror acts as a
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(a) Convex mirror of focal length 10 cm |
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(b) Concave mirror of focal length 40 cm |
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(c) Concave mirror of focal length 60 cm |
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(d) Concave mirror of focal length 10 cm |
The magnetic field due to the earth is closely equivalent to that due to
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(a) A large magnet of length equal to the diameter of the earth |
| (b) A magnetic dipole placed at the centre of the earth |
| (c) A large coil carrying current |
| (d) Neither of the above |
Assertion : Base in a transistor is made very thin as compared to collector and emitter regions.
Reason : Due to thin base power gain and voltage gain is obtained by a transistor.
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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. |
In the figure given the value of X resistance will be, when the p.d. between B and D is zero
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(a) 4 ohm |
(b) 6 ohm |
(c) 8 ohm |
(d) 9 ohm |