Atoms — Physics STD 12 Science — Question

The electric potential decreases uniformly from 120V to 80V as one moves on the x-axis from x = -1cm to x = + 1cm. The electric field at the origin.

Complete the following statements with an appropriate word/ term be filled in the blank space(s).
The force of attraction or repulsion between two charges is given by ......................

The work function of a metal is 4.2 eV, its threshold wavelength will be

(a) 4000 Å

(b) 3500 Å

(c) 2955 Å

(d) 2500 Å

The optical path of a monochromatic light is same if it goes through 4.0 cm of glass or 4.5 cm of water.  If the refractive index of glass is 1.53, the refractive index of the water is

(a) 1.30

(b) 1.36

(c) 1.42

(d) 1.46

In Young’s double slit experiment, the two slits act as coherent sources of equal amplitude A and wavelength l. In another experiment with the same set up the two slits are of equal amplitude A and wavelength l but are incoherent. The ratio of the intensity of light at the mid-point of the screen in the first case to that in the second case is

(a) 1 : 2

(b) 2 : 1

(c) 4 : 1

(d) 1 : 1

Fusion process takes place at high temperature because at high temperature :

If velocity of a particle is 3 times of that of electron and ratio of de brogile wavelength of particle to that of electron is 1.814×10⁻⁴. The particle will be:

The speed of an electron having a wavelength of  is

(a) 7.25

(b) 6.26

(c) 5.25

(d) 4.24

A ray of light is incident at an angle of 60° on one face of a prism of angle 30°. The ray emerging out of the prism makes an angle of 30° with the incident ray. The emergent ray is

(a) Normal to the face through which it emerges

(b) Inclined at 30° to the face through which it emerges

(c) Inclined at 60° to the face through which it emerges

(d) None of these

Assertion : Fax is a modulating and demodulating device.

Reason     : It is necessary for exact reproduction of a document.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If assertion is false but reason is true.