Electromagnetic Waves — Physics STD 12 Science — Question

The phenomenon of radioactivity is

(a) Exothermic change which increases or decreases with temperature

(b) Increases on applied pressure

(c) Nuclear process does not depend on external factors

(d) None of the above

A substance consisting of atoms which all have the same number of protons is called a/ an:

For the myopic eye, the defect is cured by

(a) Convex lens

(b) Concave lens

(c) Cylindrical lens

(d) Toric lens

The velocity of light in a medium is half its velocity in air.  If ray of light emerges from such a medium into air, the angle of incidence, at which it will be totally internally reflected,   is

(a) 15o

(b) 30 o

(c) 45 o

(d) 60 o

The energy of a charged capacitor resides in

(a) The electric field only	(b) The magnetic field only
(d) Neither in electric nor magnetic field	(d) Neither in electric nor magnetic field

Assertion   :   In the following circuit emf is 2V and internal resistance of the cell is 1 W and R = 1W, then reading of the voltmeter is 1V.

Reason      :  V = E - ir where E = 2V, i =  and R = 1 W

(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.

hoose the correct statement from the following:

If the speed of light were 2/3 of its present value, the energy released in a given atomic explosion will be decreased by a fraction

(a) 2/3

(b) 4/9

(c) 3/4

(d) 5/9

A double convex lens of focal length 20 cm is made of glass of refractive index 3 / 2. When placed completely in water (a,  its focal length will be

(a) 80 cm

(b) 15 cm

(c) 17.7 cm

(d) 22.5 cm

The number of turns in an air core solenoid of length 25cm and radius 4cm is 100. Its self inductance will be.