Electromagnetic Waves — Physics STD 12 Science — Question

What will be the ratio of de-Broglie wavelengths of proton and α - particle of same energy

(a) 2 : 1

(b) 1 : 2

(c) 4 : 1

(d) 1 : 4

Zener breakdown in a semi-conductor diode occurs when

(a) Forward current exceeds certain value	(b) Reverse bias exceeds certain value
(c) Forward bias exceeds certain value	(d) Potential barrier is reduced to zero

The points resembling equal potentials are

(a) P and Q

(b) S and Q

(c) S and R

(d) P and R

20 ampere current is flowing in a long straight wire. The intensity of magnetic field at a distance 10 cm from the wire will be

(a) 4 × 10–5 Wb/m2

(b) 9 × 10–5 Wb/m2

(c) 8 × 10–5 Wb/m2

(d) 6 × 10–5 Wb/m2

A charge particle is free to move in an electric field. It will travel

(a) Always along a line of force

(b) Along a line of force, if its initial velocity is zero

(c) Along a line of force, if it has some initial velocity in the direction of an acute angle with the line of force

(d) None of the above

The amplification factor of a triode valve is 15. If the grid voltage is changed by 0.3 volt the change in plate voltage in order to keep the plate current constant (in volt) is

(a) 0.02

(b) 0.002

(c) 4.5

(d) 5.0

In a semiconductor the separation between conduction band and valence band is of the order of

(a) 100 eV

(b) 10 eV

(c) 1eV

(d) 0 eV

A laser beam is used for carrying out surgery because it

(a) Is highly monochromatic	(b) Is highly coherent
(c) Is highly directional	(d) Can be sharply focussed

In a cathode ray tube, the screen is coated with fluorescent material: