Radiation and Dual Nature of Matter — Physics STD 12 Science — Question

In the hysteresis cycle, the value of H needed to make the intensity of magnetisation zero is called

(a) Retentivity

(b) Coercive force

(c) Lorentz force

(d) None of the above

If m₁ and m₂ are the refractive indices of the materials of core and cladding of an optical fibre, then the loss of light due to its leakage can be minimised by having

(a) m1 > m2

(b) m1 < m2

(c) m1 = m2

(d) None of these

Consider a planet moving in an elliptical orbit round the sun. The work done on the planet by the gravitational force of the sun:

1. Is zero in any small part of the orbit.
2. Is zero in some parts of the orbit.
3. Is zero in one complete revolution.
4. Is zero in no part of the motion.

Electromagnetic waves travel in a medium which has relative permeability 1.3 and relative permittivity 2.14. Then the speed of the electromagnetic wave in the medium will be

(a) 13.6

(b) 1.8

(c) 3.6

(d) 1.8

Two point white dots are 1mm apart on a black paper. They are viewed by eye of pupil of diameter 3mm. Approximately what is the maximum distance up to which these dots can be resolved by the eye.

An electron moving to the east in a horizontal plane is deflected towards south by a magnetic field. The direction of this magnetic field is:

If f_a and f_f represent the carrier wave frequencies for amplitude and frequency modulations respectively, then

(a)

(b)

(c)

(d)

The minimum intensity of light to be detected by human eye is  . The number of photons of wavelength  5.6   entering the eye, with pupil area  , per second for vision will be nearly

(a) 100

(b) 200

(c) 300

(d) 400

The transverse nature of light is shown by:

A diffraction is obtained by using a beam of red light. What will happen if the red light is replaced by the blue light

(a) Bands will narrower and crowd full together

(b) Bands become broader and further apart

(c) No change will take place

(d) Bands disappear