At noon the sun appears white because:
- ALight is least scattered.
- BAll the colours of the white light are scattered away.
- CBlue colour is scattered the most.
- DRed colour is scattered the most.
At noon the sun appears white because:
Explanation:
At noon because the sun is overhead, the light is scattered the least and hence appears white. When it is overhead, it has lesser air to travel through and the scattering from dust and other particles is reduced if the distance to be travelled in air is reduced.
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In Young's double slit experiment, if monochromatic light is replaced by white light
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(a) All bright fringes become white |
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(b) All bright fringes have colours between violet and red |
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(c) Only the central fringe is white, all other fringes are coloured |
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(d) No fringes are observed |
Assertion : There is no current in the metals in the absence of electric field.
Reason : Motion of free electron are randomly.
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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 cathode of a photoelectric cell is changed such that the work function changes from W1 to W2 (W2>W1). If the current before and after change are I1 and I2, all other conditions remaining unchanged, then (assuming hn > W2)
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(a) |
(b) |
(c) |
(d) |
A ball of mass 1 g and charge
moves from a point A. where potential is 600 volt to the point B where potential is zero. Velocity of the ball at the point B is 20 cm/s. The velocity of the ball at the point A will be
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(a) 22.8 cm/s |
(b) 228 cm/s |
(c) 16.8 m/s |
(d) 168 m/s |
A step index fibre has a relative refractive index of 0.88%. What is the critical angle at the corecladding interface
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(a) 60° |
(b) 75° |
(c) 45° |
(d) None of these |
The distance between charges 5 ×
and -2.7
is 0.2 m. The distance at which a third charge should be placed in order that it will not experience any force along the line joining the two charges is
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(a) 0.44 m |
(b) 0.65 m |
(c) 0.556 m |
(d) 0.350 m |
The relative permeability is represented by mr and the susceptibility is denoted by c for a magnetic substance. Then for a paramagnetic substance
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(a) mr < 1, c < 0 |
(b) mr < 1, c > 0 |
(c) mr > 1, c < 0 |
(d) mr > 1, c > 0 |