When light rays from the sun fall on a convex lens along a direction parallel to its axis
|
(a) Focal length for all colours is the same |
|
(b) Focal length for violet colour is the shortest |
|
(c) Focal length for yellow colour is the longest |
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(d) Focal length for red colour is the shortest |
(b) Focal length for violet colour is the shortest
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A closely wound coil of 100 turns and area of cross-section 
has a coefficient of self-induction 1 mH. The magnetic induction in the centre of the core of the coil when a current of 2A flows in it, will be
|
(a) |
(b) |
(c) |
(d) |
A metal rod of length 2 m is rotating with an angular velocity of 100 rad/sec in a plane perpendicular to a uniform magnetic field of 0.3 T. The potential difference between the ends of the rod is
|
(a) 30 V |
(b) 40 V |
(c) 60 V |
(d) 600 V |
A long straight wire carrying current of 30A is placed in an external uniform magnetic field of induction 4 × 10–4 T. The magnetic field is acting parallel to the direction of current. The magnitude of the resultant magnetic induction in tesla at a point 2.0 cm away from the wire is
|
(a) 10–4 |
(b) 3 × 10–4 |
(c) 5 × 10–4 |
(d) 6 × 10–4 |
The tangent galvanometer, when connected in series with a standard resistance can be used as
|
(a) An ammeter |
(b) A voltmeter |
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(c) A wattmeter |
(d) Both an ammeter and a voltmeter |
A point source of light is used in an experiment on photoelectric effect. Which of the following curves best represents the variation of photo current (i) with distance (d) of the source from the emitter
|
(a) a |
(b) b |
(c) c |
(d) d |
Ray optics fails when
|
(a) The size of the obstacle is 5 cm |
|
(b) The size of the obstacle is 3 cm |
|
(c) The size of the obstacle is less than the wavelength of light |
|
(d) (a) and (b) both |
