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

Two identical short bar magnets, each having magnetic moment M, are placed a distance of 2d apart with axes perpendicular to each other in a horizontal plane. The magnetic induction at a point midway between them is

(a)  (

(b)    (

(c)

(d) (

The first model of atom was proposed by:

Which of the following are not electromagnetic waves

(a) Cosmic rays

(b) Gamma rays

(c) b-rays

(d) X-rays

Identify the type of conductors in which both positive and negative charges can move.

The relation between the linear magnification m, the object distance u and the focal length f is

(a)

(b)

(c)

(d)

In hydrogen atom, if transition of electron from third orbit to second orbit, then wavelength of emitted radiation will be :

The ratio of de-Broglie wavelength of a a-particle to that of a proton being subjected to the same magnetic field so that the radii of their path are equal to each other assuming the field induction vector   is perpendicular to the velocity vectors of the a-particle and the proton is

(a) 1

(b)

(c)

(d) 2

The chemical equivalent of silver is 108. If the current in a silver voltameter is 2 Amp., the time required to deposit 27 grams of silver will be

(a) 8.57 hrs

(b) 6.70 hrs

(c) 3.35 hrs

(d) 12.50 hrs

A galvanometer of 50 ohm resistance has 25 divisions. A current of 4 × 10^–4 ampere gives a deflection of one division. To convert this galvanometer into a voltmeter having a range of 25 volts, it should be connected with a resistance of

(a) 2500 W as a shunt	(b) 2450 W as a shunt
(c) 2550 W in series	(d) 2450 W in series

The transistor are usually made of: