Dual Nature of Radiation and Matter — Physics STD 12 Science — Question

According to Bohr's model, the radius of the second orbit of helium atom is

(a) 0.53 Å

(b) 1.06 Å

(c) 2.12 Å

(d) 0.265 Å

For measurement of potential difference, potentiometer is preferred in comparison to voltmeter because

(a) Potentiometer is more sensitive than voltmeter

(b) The resistance of potentiometer is less than voltmeter

(c) Potentiometer is cheaper than voltmeter

(d) Potentiometer does not take current from the circuit

Which of the following group is diamagnetic?

The magnitude of magnifying power of an astronomical telescope is 5, the focal power of its eyepiece is 10 diopters. The focal power of its objective (in diopters) is:

A transformer has turn ratio 100/1. If secondary coil has 4 amp current then current in primary coil is

(a) 4 A

(b) 0.04 A

(c) 0.4 A

(d) 400 A

An electron moving with a velocity of 15ms^-1 enters a uniform magnetic field of 0.2 T, along a direction parallel to the field. What would be its trajectory in this field?

The SI unit of volume charge density is:

A small square loop of wire of side l is placed inside a large square loop of wire of side L (L > l). The loop are coplanar and their centre coincide. The mutual inductance of the system is proportional to

(a) l / L

(b)

(c) L/l

(d)

Two lithium nuclei in a lithium vapour at room temperature do not combine to form a carbon nucleus because:

1. A lithium nucleus is more tightly bound than a carbon nucleus.
2. Carbon nucleus is an unstable particle.
3. It is not energetically favourable.
4. Coulomb repulsion does not allow the nuclei to come very close.

A silicon speciman is made into a P-type semi-conductor by dopping, on an average, one Indium atom per 5  silicon atoms. If the number density of atoms in the silicon specimen is 5   then the number of acceptor atoms in silicon per cubic centimetre will be

(a) 2.5	(b) 1.0
(c) 1.0	(d) 2.5