Question
A ray is reflected in turn by three plain mirrors mutually at right angles to each other. The angle between the incident and the reflected rays is
| (a) 90° | (b) 60° | (c) 180° | (d) None of these |
A ray is reflected in turn by three plain mirrors mutually at right angles to each other. The angle between the incident and the reflected rays is
| (a) 90° | (b) 60° | (c) 180° | (d) None of these |
(c) 180°
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Focal length of a convex lens will be maximum for
|
(a) Blue light |
(b) Yellow light |
(c) Green light |
(d) Red light |
A 20F capacitor is charged to 5V and isolated. It is then connected in parallel with an uncharged 30F capacitor. The decrease in the energy of the system will be
|
(a) 25 J |
(b) 200 J |
(c) 125 J |
(d) 150 J |
The maximum illumination on a screen at a distance of 2 m from a lamp is 25 lux. The value of total luminous flux emitted by the lamp is
|
(a) 1256 lumen |
(b) 1600 lumen |
(c) 100 candela |
(d) 400 lumen |
A cut diamond sparkles because of its
|
(a) Hardness |
(b) High refractive index |
|
(c) Emission of light by the diamond |
(d) Absorption of light by the diamond |