Atoms — Physics STD 12 Science — Question

Total internal reflection of a ray of light is possible when the ( = critical angle, i  =  angle of incidence)

(a) Ray goes from denser medium to rarer medium and

(b) Ray goes from denser medium to rarer medium and

(c) Ray goes from rarer medium to denser medium and

(d) Ray goes from rarer medium to denser medium and

Assertion  : When PN-junction is forward biased then motion of charge carriers at junction is due to diffusion. In reverse biasing. The cause of motion of charge is drifting.

Reason     : In the following circuit emitter is reverse biased and collector is forward biased.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

Flux passing through an equipotential surface is always:

Resistance in the two gaps of a meter bridge are 10 ohm and 30 ohm respectively. If the resistances are interchanged the balance point shifts by

(a) 33.3 cm

(b) 66.67cm

(c) 25 cm

(d) 50 cm

Speed of light is maximum in

(a) Water

(b) Air

(c) Glass

(d) Diamond

The capacitance of a parallel plate condenser does not depend on

(a) Area of the plates	(b) Medium between the plates
(c) Distance between the plates	(d) Metal of the plates

Which of the following plots may represent the thermal energy produced in a resistor in a given time as a function of the electric current

(a) a

(b) b

(c) c

(d) d

A ray of light is incident on a transparent glass slab of refractive index 1.62.  The reflected and the refracted rays are mutually perpendicular. The angle of incidence is

(a) 58.3o

(b) 50o

(c) 35o

(d) 30o

A nuclear reaction with positive Q value is: