Magnetism And Matter — Physics STD 12 Science — Question

An oscillator is producing FM waves of frequency 2 kHz with a variation of 10 kHz. What is the modulating index

(a) 0.20

(b) 5.0

(c) 0.67

(d) 1.5

The sum of all electromagnetic forces between different particles of a system of charged particles is zero:

1. Only if all the particles are positively charged.
2. Only if all the particles are negatively charged.
3. Only if half the particles are positively charged and half are negatively charged.
4. Irrespective of the signs of the charges.

The curves (a), (b) (c) and (d) show the variation between the applied potential difference (V) and the photoelectric current (i), at two different intensities of light (I₁ > I₂). In which figure is the correct variation shown

(a)

(b)

(c)

(d)

A double charged lithium atom is equivalent to hydrogen whose atomic number is 3. The wavelength of required radiation for emitting electron from first to third Bohr orbit in   will be (Ionisation energy of hydrogen atom is 13.6eV)

(a) 182.51 Å

(b) 177.17 Å

(c) 142.25 Å

(d) 113.74 Å

Bonding in a germanium crystal (semi- conductor) is

(a) Metallic

(b) Ionic

(c) Vander Waal's type

(d) Covalent

A paramagnetic material is kept in a magnetic field. The field is increased till the magnetization becomes constant. If the temperature is now decreased, the magnetization:

A nucleus of an element  emits an a-particle first, a b-particle next and then a gamma photon. The final nucleus formed has an atomic number

(a) 200

(b) 199

(c) 83

(d) 198

A conductor of 3 m in length is moving perpendicularly to magnetic field of  tesla with the speed of , then the e.m.f. produced across the ends of conductor will be

(a)  0.03 volt

(b) 0.3 volt

(c) 3 ×

(d) 3 volt

The ratio of the intensity at the centre of a bright fringe to the intensity at a point one-quarter of the distance between two fringe from the centre is

(a) 2

(b) 1/2

(c) 4

(d) 16