Which of the following quantities increase when wavelength is increased? Consider only the magnitudes.
Explanation:
The focal length of a lens is inversely proportional to the refractive index of the lens and the refractive index of the lens is inversely proportional to the square of wavelength. Therefore, the focal length is directly dependent on wavelength; it increases when the wavelength is increased.
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In a parallel plate condenser, the radius of each circular plate is 12 cm and the distance between the plates is 5mm. There is a glass slab of 3mm thick and of radius 12 cm with dielectric constant 6 between its plates. The capacity of the condenser will be
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(a) 144 |
(b) 40 pF |
(c) 160 pF |
(d) 1.44 μF |
Two identical short bar magnets, each having magnetic moment of 10 Am2, are arranged such that their axial lines are perpendicular to each other and their centres be along the same straight line in a horizontal plane. If the distance between their centres is 0.2 m, the resultant magnetic induction at a point midway between them is (
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(a) |
(b) |
(c)  Tesla
|
(d)  Tesla
|
The reason of current flow in P-N junction in forward bias is
|
(a) Drifting of charge carriers |
(b) Minority charge carriers |
|
(c) Diffusion of charge carriers |
(d) All of these |
Two like magnetic poles of strength 10 and 40 SI units are separated by a distance 30 cm. The intensity of magnetic field is zero on the line joining them
|
(a) At a point 10 cm from the stronger pole |
|
(b) At a point 20 cm from the stronger pole |
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(c) At the mid-point |
|
(d) At infinity |
If the critical angle for total internal reflection from a medium to vacuum is 30°, the velocity of light in the medium is
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(a) 3 |
(b) 1.5 |
(c) 6 |
(d) |
A dielectric slab of thickness d is inserted in a parallel plate capacitor whose negative plate is at x = 0 and positive plate is at x = 3d. The slab is equidistant from the plates. The capacitor is given some charge. As one goes from 0 to 3d
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(a) The magnitude of the electric field remains the same |
|
(b) The direction of the electric field remains the same |
|
(c) The electric potential increases continuously |
|
(d) b, c |
