A diverging beam of light from a point source S having divergence angle a, falls symmetrically on a glass slab as shown. The angles of incidence of the two extreme rays are equal. If the thickness of the glass slab is t and the refractive index n, then the divergence angle of the emergent beam is
|
(a) Zero |
(b) α |
(c) |
(d) 2 |
(b) α
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Two infinite length wires carries currents 8A and 6A respectively and placed along X and Y-axis. Magnetic field at a point P(0, 0, d)m will be
|
(a) |
(b) |
(c) |
(d) |
The photoelectric threshold wavelength for potassium (work function being 2eV ) is
|
(a) 310 nm |
(b) 620 nm |
(c) 1200 nm |
(d) 2100 nm |
In Young's experiment, light of wavelength 4000 Å is used to produce bright fringes of width 0.6 mm, at a distance of 2 meters. If the whole apparatus is dipped in a liquid of refractive index 1.5, then fringe width will be
|
(a) 0.2 mm |
(b) 0.3 mm |
(c) 0.4 mm |
(d) 1.2 mm |
A body of capacity 4μF is charged to 80 V and another body of capacity 6μF is charged to 30V. When they are connected the energy lost by 4 μF capacitor is
|
(a) 7.8 mJ |
(b) 4.6 mJ |
(c) 3.2 mJ |
(d) 2.5 mJ |
As the electron in Bohr orbit of Hydrogen atom passes from state n = 2 to n = 1, the kinetic energy K and potential energy U change as
|
(a) K two-fold, U four-fold |
(b) K four-fold, U two-fold |
|
(c) K four-fold, U also four-fold |
(d) K two-fold, U also two-fold |
There is a current of 20 amperes in a copper wire of 
square metre area of cross-section. If the number of free electrons per cubic metre is 
, then the drift velocity is
|
(a) 125 |
(b) 12.5 |
(c) 1.25 |
(d) 1.25 |
