- AAll points are in the same phase.
- BThere is a pair of points in opposite phase.
- CThere is a pair of points with phase difference $(\frac{\pi}{2})$.
- DThere is no relation between the phases.
Explanation:
A wavefront is the locus of points characterized by propagation of position of the same phase:
a propagation of a line in 1D, a curve in 2D or a surface for a wave in 3D.
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Assertion : The speed of light in a rarer medium is greater than that in a denser medium
Reason : One light year equals to 9.5 × 1012 km
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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. |

The rays of different colours fail to converge at a point after going through a converging lens. This defect is called:
A screen is placed a distance 40cm away from an illuminated object. A converging lens is placed between the source and the screen and it is attempted to form the image of the source on the screen. If no position could be found, the focal length of the lens:
An infinite number of charges, each of charge 1 mC, are placed on the x-axis with co-ordinates x = 1, 2, 4, 8, ....¥. If a charge of 1 C is kept at the origin, then what is the net force acting on 1 C charge
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(a) 9000 N |
(b) 12000 N |
(c) 24000 N |
(d) 36000 N |
Assertion : Electron capture occurs more often than positron emission in heavy elements.
Reason : Heavy elements exhibit radioactivity.
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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 : Silicon is preferred over germanium for making semiconductor devices.
Reason : The energy gap for germanium is more than the energy gap of silicon.
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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. |
The electric intensity due to a dipole of length 10 cm and having a charge of 500μC, at a point on the axis at a distance 20 cm from one of the charges in air, is
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(a) 6.25 |
(b) 9.28 |
(c) 13.1 |
(d) |