Electromagnetic Waves — Physics STD 12 Science — Question

White light may be considered to be a mixture of waves with l ranging between 3900 Å and 7800 Å. An oil film of thickness 10,000 Å is examined normally by reflected light. If m = 1.4, then the film appears bright for

(a) 4308 Å, 5091 Å, 6222 Å	(b) 4000 Å, 5091 Å, 5600 Å
(c) 4667 Å, 6222 Å, 7000 Å	(d) 4000 Å, 4667 Å, 5600 Å, 7000Å

The solar constant on the surface of the earth is S. What will be its value on the surface of another planet which is about 5.3 A.U. away from sun

(a)

(b)

(c) 5.3 S

(d) (5.3)2 S

In series L - C - R resonant circuit, to increase the resonant frequency:

Two long straight wires are set parallel to each other. Each carries a current i in the same direction and the separation between them is 2r. The intensity of the magnetic field midway between them is

(a)

(b) 4

(c) Zero

(d)

Young's experiment is performed in air and then performed in water, the fringe width

(a) Will remain same

(b) Will decrease

(c) Will increase

(d) Will be infinite

Which of the following is the best insulator?

The amplification factor of a triode is 20. If the grid potential is reduced by 0.2 volt then to keep the plate current constant its plate voltage is to be increased by

(a) 10 volt

(b) 4 volt

(c) 40 volt

(d) 100 volt

In a nuclear reaction, which of the following is conserved

(a) Atomic number

(b) Mass number

(c) Atomic number, mass number and energy

(d) None of these

When was Van de Graff generator invented and by whom?

The relationship between potential difference V, charge Q and capacitance C is: