In Young’s double slit experiment, a minimum is obtained when the phase difference of super imposing waves is
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(a) Zero |
(b) (2n – 1)π |
(c) nπ |
(d) (n + 1) π |
(b) (2n – 1)π
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The figure represents the observed intensity of X-rays emitted by an X-ray tube as a function of wavelength. The sharp peaks A and B denote
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(a) Band spectrum |
(b) Continuous spectrum |
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(c) Characteristic radiations |
(d) White radiations |
Two cells, e.m.f. of each is E and internal resistance r are connected in parallel between the resistance R. The maximum energy given to the resistor will be, only when
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(a) R = r/2 |
(b) R = r |
(c) R = 2r |
(d) R = 0 |
Missing lines in a continuous spectrum reveal
|
(a) Defects of the observing instrument |
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(b) Absence of some elements in the light source |
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(c) Presence in the light source of hot vapours of some elements |
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(d) Presence of cool vapours of some elements around the light source |
Unpolarized light falls on two polarizing sheets placed one on top of the other. What must be the angle between the characteristic directions of the sheets if the intensity of the final transmitted light is one-third the maximum intensity of the first transmitted beam
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(a) 75° |
(b) 55° |
(c) 35° |
(d) 15° |
The heat produced by a 100 watt heater in 2 minute will be equal to
|
(a) 12 |
(b) 10 |
(c) 6 |
(d) 3 |
Doppler's effect in sound in addition to relative velocity between source and observer, also depends while source and observer or both are moving. Doppler effect in light depend only on the relative velocity of source and observer. The reason of this is
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(a) Einstein mass - energy relation |
(b) Einstein theory of relativity |
|
(c) Photoelectric effect |
(d) None of these |
In a Young's double slit experiment the source S and the two slits A and B are vertical with slit A above slit B. The fringes are observed on a vertical screen K. The optical path length from S to B is increased very slightly (by introducing a transparent material of higher refractive index) and the optical path length from S to A is not changed, as a result the fringe system on K moves
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(a) Vertically downwards slightly |
(b) Vertically upwards slightly |
|
(c) Horizontally, slightly to the left |
(d) Horizontally, slightly to the right |
Assertion : X-ray travel with the speed of light.
Reason : X-rays are electromagnetic rays.
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(a) If both assertion and reason are true and the reason is the correct explanation of the assertion. |
|
(b) If both assertion and reason are true but reason is not the correct explanation of the assertion. |
|
(c) If assertion is true but reason is false. |
|
(d) If the assertion and reason both are false. |
