Wave Optics — Physics STD 12 Science — Question

The variation of magnetic susceptibility (x) with temperature for a diamagnetic substance is best represented by

(a)

(b)

(c)

(d)

The electron cannot exist inside the nucleus because:

The current in a LR circuit builds up to  th of its steady state value in 4s. The time constant of this circuit is

(a)

(b)

(c)

(d)

In an insulator, the forbidden energy gap between valence band and conduction band is of the following order :

In a parallel beam of white light is incident on a converging lens, the colour which is brought to focus nearest to the lens is

(a) Violet	(b) Red
(c) The mean colour	(d) All the colours together

Comment on the statement given below:
In self-inductionWhen the current in a coil is increasing, induced emf opposes it
When the current in a coil is decreasing, induced emf supports it

The potentials of the two plates of capacitor are +10V and –10 V. The charge on one of the plates is 40 C. The capacitance of the capacitor is

(a) 2 F

(b) 4 F

(c) 0.5 F

(d) 0.25 F

The coercivity of a small magnet where the ferromagnet gets demagnetized is 3 × 10³ Am^–1. The current required to be passed in a solenoid of length 10cm and number of turns 100, so that the magnet gets demagnetized when inside the solenoid, is:

In X-ray experiment K_a, K_b denotes

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

A uniform wire is bent in the form of a circle of radius R. A current I enters at A and leaves at C as shown in the figure :

If the length ABC is half of the length ADC, the magnetic field at the centre O will be

(a) Zero

(b)

(c)

(d)