Geometrical Optics — Physics STD 12 Science — Question

The area of the plates of a parallel plate condenser is A and the distance between the plates is 10 mm. There are two dielectric sheets in it, one of dielectric constant 10 and thickness 6mm and the other of dielectric constant 5 and thickness 4mm. The capacity of the condenser is

(a)

(b)

(c)

(d) 1500

In order to quadruple the resistance of a uniform wire, a part of its length was uniformly stretched till the final length of the entire wire was 1.5 times the original length, the part of the wire was fraction equal to

(a) 1 / 8

(b) 1 / 6

(c) 1 / 10

(d) 1 / 4

A milliammeter of range 10 mA has a coil of resistance 1 W.  To use it as voltmeter of range 10 volt, the resistance that must be connected in series with it, will be

(a) 999 W

(b) 99 W

(c) 1000 W

(d) None of these

When a photon stimulates the emission of another photon, the two photons have:

A body has its centre of mass at the origin. the x-coordinates of the particles:

1. May be all positive.
2. May be all negative.
3. May be all non-negative.
4. May be positive for some cases and negative in other cases.

If the speed of light were 2/3 of its present value, the energy released in a given atomic explosion will be decreased by a fraction

(a) 2/3

(b) 4/9

(c) 3/4

(d) 5/9

The equivalent resistance between points A and B of an infinite network of resistances each of 1Ω connected as shown, is

(a) Infinite

(b) 2 Ω

(c)

(d) Zero

Half life of  is  5 days. If we start with 50,000  atoms of this isotope, the number of atoms left over after 10 days is

(a) 5,000

(b) 25,000

(c) 12,500

(d) 20,000

The focal length of the objective of a compound microscope if f_o and its distance from the eyepiece is L. The object is placed at a distance u from the objective. For proper working of the instrument:

1. L < u
2. L > u
3. f_o < L < 2f_o
4. L > 2f_o