Electromagnetic Waves — Physics STD 12 Science — Question

The depletion layer in the P-N junction region is caused by

(a) Drift of holes	(b) Diffusion of charge carriers
(c) Migration of impurity ions	(d) Drift of electrons

PQRS is a square loop made of uniform conducting wire the current enters the loop at P and leaves at S.  Then the magnetic field will be

(a) Maximum at the centre of the loop	(b) Zero at the centre of loop
(c) Zero at all points inside the loop	(d) Zero at all points outside of the loop

The threshold wavelength for photoelectric effect of a metal is 6500 Å. The work function of the metal is approximately

(a) 2 eV

(b) 1 eV

(c) 0.1 eV

(d) 3 eV

A player with 3 m long iron rod runs towards east with a speed of 30 km/hr. Horizontal component of earth's magnetic field is 4 . If he is running with rod in horizontal and vertical positions, then the potential difference induced between the two ends of the rod in two cases will be

(a) Zero in vertical position and 1  in horizontal position

(b) 1  in vertical position and zero is horizontal position

(c) Zero in both cases

(d) 1  in both cases

Which of the following phenomena can be demonstrated by light. But not with sound waves in an air column? 

The two ends of a uniform conductor are joined to a cell of e.m.f. E and some internal resistance. Starting from the midpoint P of the conductor, we move in the direction of current and return to P. The potential V at every point on the path is plotted against the distance covered (x). Which of the following graphs best represents the resulting curve

(a)

(b)

(c)

(d)

To measure which of the following, is a tangent galvanometer used

(a) Charge

(b) Angle

(c) Current

(d) Magnetic intensity

Penetrating power of X-rays does not depend on

(a) Wavelength	(b) Energy
(c) Potential difference	(d) Current in the filament

The field due to a long straight wire carrying a current I is proportional to

(a) I

(b)

(c)

(d) 1/I