Nuclei — Physics STD 12 Science — Question

Polarization of light confirms :

Magnetic permeability is maximum for

(a) Diamagnetic substance	(b) Paramagnetic substance
(c) Ferromagnetic substance	(d) All of these

Energy in the sun is generated mainly by

(a) Fusion of radioactive material	(b) Fission of helium atoms
(c) Chemical reaction	(d) Fusion of hydrogen atoms

A beam of light propagating in medium A with index of refraction n (A) passes across an interface into medium B with index of refraction n(B). The angle of incidence is greater than the angle of refraction; v(A) and v(B) denotes the speed of light in A and B. Then which of the following is true

(a) v(A) > v(B)  and n(A) > n(B)	(b) v(A) > v(B)  and  n(A) < n(B)
(c) v(A) < v(B)  and  n(A) > n(B)	(d) v(A) < v(B)  and  n(A) < n(B)

A vertical wire carrying a current in the upward direction is placed in horizontal magnetic field directed towards north. The wire will experience a force directed towards

(a) North

(b) South

(c) East

(d) West

Which one of the following is not electromagnetic in nature

(a) X-rays

(b) Gamma rays

(c) Cathode rays

(d) Infrared rays

A varying current in a coil changes from 10 amp to zero in 0.5 sec. If average EMF is induced in the coil is 220 volts, the self inductance of coil is

(a) 5 H

(b) 10 H

(c) 11 H

(d) 12 H

The mass number of He is 4 and that for sulphur is 32. The radius of sulphur nucleus is larger than that of helium, by times

(a)

(b) 4

(c) 2

(d) 8

Light from a hydrogen discharge tube is incident on the cathode of a photoelectric cell the work function of the cathode surface is 4.2 eV. In order to reduce the photo-current to zero the voltage of the anode relative to the cathode must be made

(a) – 4.2 V

(b) – 9.4 V

(c) – 17.8 V

(d) +9.4 V

What is the net magnetic flux through a closed surface?