While using an electric bulb, the reflection for street lighting should be from
|
(a) Concave mirror |
(b) Convex mirror |
(d) Parabolic mirror |
(d) Parabolic mirror |
(b) Convex mirror
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The working of optical instruments like camera, microscope, telescope, etc. having glass lenses is based on a phenomenon of light. Identify the phenomenon.
Two bulbs of 500 watt and 200 watt are manufactured to operate on 220 volt line. The ratio of heat produced in 500 W and 200 W, in two cases, when firstly they are joined in parallel and secondly in series, will be
|
(a) |
(b) |
(c) |
(d) |
If m is mass of electron, v its velocity, r the radius of stationary circular orbit around a nucleus with charge Ze, then from Bohr's first postulate, the kinetic energy K = 
of the electron in C.G.S. system is equal to
|
(a) |
(b) |
(c) |
(d) |
With the increase in principle quantum number, the energy difference between the two successive energy levels
|
(a) Increases |
|
(b) Decreases |
|
(c) Remains constant |
|
(d) Sometimes increases and sometimes decreases |
A 50 volt potential difference is suddenly applied to a coil with 
henry and R = 180 ohm. The rate of increase of current after 0.001 second is
|
(a) 27.3 amp/sec |
(b) 27.8 amp/sec |
(c) 2.73 amp/sec |
(d) None of the above |
In Bohr model of the hydrogen atom, the lowest orbit corresponds to
|
(a) Infinite energy |
(b) The maximum energy |
|
(c) The minimum energy |
(d) Zero energy |
If there are n capacitors in parallel connected to V volt source, then the energy stored is equal to
|
(a) CV |
(b) |
(c) |
(d) |
A convex lens is used to form real image of an object on a screen. It is observed that even when the positions of the object and that screen are fixed there are two positions of the lens to form real images. If the heights of the images are 4 cm and 9 cm respectively, the height of the object is
|
(a) 2.25 cm |
(b) 6.00 cm |
(c) 6.50 cm |
(d) 36.00 cm |
