Wave Optics — Physics STD 12 Science — Question

In which one of the following regions of the electromagnetic spectrum will the vibrational motion of molecules give rise to absorption

(a) Ultraviolet

(b) Microwaves

(c) Infrared

(d) Radio waves

Choose the wrong statement of the following:

The brightness of a bulb will be reduced, if a resistance is connected in

(a) Series with it	(b) Parallel with it
(c) Series or parallel with it	(d) Brightness of the bulb cannot be reduced

The radius of two metallic spheres A and B  are  and  respectively (. They are connected by a thin wire and the system is given a certain charge. The charge will be greater

(a) On the surface of the sphere B	(b) On the surface of the sphere  A
(c) Equal on both	(d) Zero on both

A proton and an electron enter a region with equal speed in which a magnetic field is suddenly switched on. The force experienced by them are:

One serious drawback of semi-conductor devices is:

A non-planar loop of conducting wire carrying a current I is placed as shown in the figure. Each of the straight sections of the loop is of length 2a. The magnetic field due to this loop at the point P (a,0,a) points in the direction

(a)

(b)

(c)

(d)

In the figure shown, the total resistance between A and B is

(a) 12 Ω

(b)  4 Ω

(c)  6 Ω

(d) 8 Ω

A charge Q is divided into two parts of q  and Q - q. If the coulomb repulsion between them when they are separated is to be maximum, the ratio of   should be

(a) 2

(b) 1/2

(c) 4

(d) 1/4

An α- particle travels in a circular path of radius 0.45 m in a magnetic field  B = 1.2  with a speed of 2.6 . The period of revolution of the α -  particle is

(a) 1.1

(b) 1.1

(c) 1.1

(d) 1.1