Atoms — Physics STD 12 Science — Question

When you speak to your friend, which of the following parameters have a unique value in the sound produced?

1. Frequency.
2. Wavelength.
3. Amplitude.
4. Wave velocity.

In an intrinsic semiconductor, the number of electrons in the conduction band is ________ the number of holes in the valence band.

Four condensers are joined as shown in the adjoining figure. The capacity of each is 8 μF. The equivalent capacity between the points A and  B will be

(a) 32  μF

(b) 2 μF

(c) 8 μF

(d) 16 μF

A small lamp is hung at a height of 8 feet above the centre of a round table of diameter 16 feet. The ratio of intensities of illumination at the centre and at points on the circumference of the table will be

(a) 1 : 1

(b) 2 : 1

(c) 2

(d) 3 : 2

Arrange the following in the increasing order of magnetic susceptibility.

A current of 1 mA is flowing through a copper wire.  How many electrons will pass a given point in one second [e = 1.6 × 10^–19 Coulomb]

(a) 6.25 ×

(b) 6.25 ×

(c) 6.25 ×

(d) 6.25 ×

How did de – Broglie conclude the modification of Bohr’s II postulate?

Two charges each of 1 coulomb are at a distance 1 km  apart, the force between them is

(a)	(b) 9
(c)	(d)

The graph which represents the correct variation of logarithm of activity (log A) versus time, in figure is

(a) A

(b) B

(c) C

(d) D

In hydrogen atom the angular momentum of electron in ground energy state is :