Explanation:
Line respectrum is characteristic of the element because it obtained of atoms only. Continous spectrum is characteristics of the source of light.
In the spectrum of sodium, there are two prominent yellow lines of wavelength 589.0 nm and 589.6 nm.
Absorption line spectrum is not characteristic of the element.
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Assertion : We can measure the potential barrier of a PN junction by putting a sensitive voltmeter across its terminals.
Reason : The current through the PN junction is not same in forward and reversed bias.
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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. |
Constantan wire is used in making standard resistances because its
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(a) Specific resistance is low |
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(b) Density is high |
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(c) Temperature coefficient of resistance is negligible |
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(d) Melting point is high |
A transparent cube of 15 cm edge contains a small air bubble. Its apparent depth when viewed through one face is 6 cm and when viewed through the opposite face is 4 cm. Then the refractive index of the material of the cube is
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(a) 2.0 |
(b) 2.5 |
(c) 1.6 |
(d) 1.5 |
Two rails of a railway track insulated from each other and the ground are connected to a milli voltmeter. What is the reading of voltmeter, when a train travels with a speed of 180 km/hr along the track. Given that the vertical component of earth's magnetic field is 0.2 
and the rails are separated by 1 metre
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(a) |
(b) |
(c) |
(d) 1 volt |
The frequency of a light ray is 6 
. Its frequency when it propagates in a medium of refractive index 1.5, will be
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(a) 1.67 |
(b) 9.10 |
(c) 6 |
(d) 4 |
