Ray Optics and Optical Instruments — Physics STD 12 Science — Question

The drift velocity does not depend upon

(a) Cross-section of the wire	(b) Length of the wire
(c) Number of free electrons	(d) Magnitude of the current

Two nuclei have their mass numbers in the ratio of 1:27. The ratio of their nuclear densities are-

A solid conducting sphere of radius a has a net positive charge 2Q. A conducting spherical shell of inner radius  b and outer radius c is concentric with the solid sphere and has a net charge – Q. The surface charge density on the inner and outer surfaces of the spherical shell will be

(a)

(b)

(c) 0,

(d) None of the above

In P-type semiconductor, there is

(a) An excess of one electron	(b) Absence of one electron
(c) A missing atom	(d) A donar level

Which of the following statements indicates that light waves are transverse

(a) Light waves can travel in vacuum	(b) Light waves show interference
(c) Light waves can be polarized	(d) Light waves can be diffracted

The equivalent resistance of the following infinite network of resistances is

(a) Less than 4 Ω	(b) 4 Ω
(c) More than 4 Ω  but less than 12 Ω	(d) 12 Ω

Vapour is injected at a uniform rate in a closed veseel which was initially evacuated. The pressure in the vessel:

1. Increaaes continuously.
2. Decreases continuously.
3. First increases and then decreases.
4. First increases and then becomes constant.

Two coherent sources of light can be obtained by

(a) Two different lamps

(b) Two different lamps but of the same power

(c) Two different lamps of same power and having the same colour

(d) None of the above

In Young’s double slit experiment, a minimum is obtained when the phase difference of super imposing waves is

(a) Zero

(b) (2n – 1)π

(c) nπ

(d)  (n + 1) π

A parallel plate condenser is filled with two dielectrics as shown. Area of each plate is  and the separation is t metre . The dielectric constants are   and  respectively. Its capacitance in farad will be

(a)

(b)

(c)

(d)