Ray Optics and Optical Instruments — Physics STD 12 Science — Question

The sun is rotating about its own axis. The spectral lines emitted from the two ends of its equator, for an observer on the earth, will show

(a) Shift towards red end

(b) Shift towards violet end

(c) Shift towards red end by one line and towards violet end by other

(d) No shift

Four wires each of length 2.0 metres are bent into four loops P, Q, R and S and then suspended into uniform magnetic field. Same current is passed in each loop. Which statement is correct

(a) Couple on loop P will be the highest	(b) Couple on loop Q will be the highest
(c) Couple on loop R will be the highest	(d) Couple on loop S will be the highest

A ray passes through a prism of angle 60° in minimum deviation position and suffers a deviation of 30°. What is the angle of incidence on the prism

(a) 30°

(b) 45°

(c) 60°

(d) 90°

An electric dipole consisting of two opposite charges of 2   each separated by a distance of 3 cm is placed in an electric field of 2  N/C. The maximum torque on the dipole will be

(a) 12

(b) 12

(c) 24

(d) 24

Huygen's conception of secondary waves

(a) Allow us to find the focal length of a thick lens

(b) Is a geometrical method to find a wavefront

(c) Is used to determine the velocity of light

(d) Is used to explain polarisation

The half-life of radioactive Polonium (Po) is 138.6 days. For ten lakh Polonium atoms, the number of disintegrations in 24 hours is

(a) 2000

(b) 3000

(c) 4000

(d) 5000

Consider a simple circuit shown in Fig. stands for a variable resistance R'. R' can vary from R₀ to infinity. r is internal resistance of the battery (r < < R < < R₀).

The S.I. unit of electric flux is

(a) Weber	(b) Newton per coulomb
(c) Volt  × metre	(d) Joule per coulomb

In X-ray experiment K_a, K_b denotes

(a) Characteristic	(b) Continuous wavelength
(c) a, b-emissions respectively	(d) None of these

A circular coil of mean radius of 7 cm and having 4000 turns is rotated at the rate of 1800 revolutions per minute in the earth's magnetic field (B = 0.5 gauss), the maximum e.m.f. induced in coil will be

(a) 1.158 V

(b) 0.58 V

(c) 0.29 V

(d) 5.8 V