# Electromagnetic waves Questions and Answers

Physics

Electromagnetic wavesa infrared point source S of power 1 25 kW as shown in the figure The lateral surface of the rod is perfectly insulated from the surroundings If the cross section A absorbs 80 of the AAJ KA TOPPER incident energy and the temperature difference between the ends of the rod is constant then the rate of heat flow through the rod in steady state is

Physics

Electromagnetic wavesA transmitting antenna of a radio station is mounted vertically At a point 10 km due north of the transmitter the peak value of electric field is 10 V m The magnitude of magnetic field at that location in gauss is 3 33 3 33 10 8 3 33 10 12 hr min 3 33 10 5

Physics

Electromagnetic wavesFind force exerted by light beam of intensity I incident on a cylinder height h and base radius R placed on surface as shown in figure Cylinder is having reflection coefficient 0 8 assum transmission A 38 7Rh 15 C

Physics

Electromagnetic wavesFigure shows a cylinder containing helium gas at atmospheric pressure with a tightly fitting piston of weight one fourth the force acting due to atmospheric pressure The cylinder is jammed at its bottom A block B is hung by means of a mass less string whose other end is attached to the piston It is observed that the piston just starts sliding next the block B is directly placed above the piston Assuming the piston to move slowly find the fractional volume of the gas compressed fixed A C D

Physics

Electromagnetic wavestwo circular plates each of radius r 12 cm and separated by d 5 0 mm The capacitor is being charged by an external source The charging current is constant current I 0 15 A 00 Find the displacement current across the plates a 1 5 A 015 A

Physics

Electromagnetic wavesSachin Tendulkar A projects a ball of mass m towards Virendra Sehwag B of mass 48 m as shown in figure The ball collides with the two vertical walls and when it just passes the wall W its velocity is horizontal Sehwag is standing on a cart of mass m catches the ball at the same level at which the ball is projected After the catch cart starts moving with a velocity 0 3 m s horizontally towards right The initial velocity vector of projection of ball is given by V 10 21 1 m s Find the value of Walls are smooth and there is no friction between cart and ground Sehwag remains fixed with respect to the cart Coefficient of restitution of ball with the walls and the required height is shown in the figure W www 1 2 Am 0 3 4 49m

Physics

Electromagnetic wavesT The dielectric wavelength constant of a gas of is given the following equation here c is the speed of light in free space and v is the phase velocity Then the group velocity V when v 0 1c is given by b j 5 2 C V 2 1 0 5 2 0 222

Physics

Electromagnetic wavesIn the arrangement shown in the figure there is a horizontal cylindrical uniform but time varying magnetic field increasing at a constant rate A charge particle having charge q and mass m is kept in equilibrium at the top of a spring of spring constant k in such a way that it is on the horizontal line passing through the centr of the magnetic field as shown in figure If the compression in the spring is x the constant rate of varying magnetic field is A B 21 3qR D kx mg 21 qR2kx mg 21 C kx mg qR 51 4qR kx mg reeeer q k AM

Physics

Electromagnetic wavesAn electromagnetic wave has an electric field given by E y t Ex y t 100 0 cos 20y wt where everything is in mks units a What is w b What is the frequency f c What is the wavelength d What is B y t e What is the average energy density of the wave

Physics

Electromagnetic wavesAn emf of 20 V is applied at time t 0 to a circuit containing in series 10 mH inductor and 52 resistor The ratio of the currents at time t and at t 40 s is close to Take e 7 389 1 1 06 2 1 15 3 1 46 4 0 84 T B

Physics

Electromagnetic wavesA planar loop of wire rotates in a uniform magnetic field Initially at t 0 the plane of the loop is perpendicular to the magnetic field If it rotates with a period of 10 s about an axis in its plane then the magnitude of induced emf will be maximum and minimum respectively

Physics

Electromagnetic wavesd 2 5 104 26 The sun radiates electromagnetic energy at the rate of 3 9 x 1026 W Its radius is 6 96 x 108 m The intensity of sun light in W m at the solar surface will be a 5 6 106 b 6 4 107 c 4 2 106 d 4 2 107

Physics

Electromagnetic waves3 The amplitude of the sinusoidally oscillating electric field of plane wave is 60 V m Then the amplitude of the magnetic field is a 2 10 T c 6 10 T b 6 10 T d 2 10 T

Physics

Electromagnetic wavesA charge Q is placed on the surface of an original and charged soap bubble of radius r Because of the mutual repulsion of the charged surface the radius increases to a somewhat larger radius R If p be the atmospheric pressure The work done by the bubble in pushing back the atmosphere is given by

Physics

Electromagnetic wavesm2 d 2 3 x 10 W m2 12 The magnetic field of a beam emerging from a filter facing a flood light is given by 3 W B 12 x 10 8 sin 1 20 x 107 z 3 60 x average intensity of the beam is a 1 71 Wm2 b 2 1 W m 2 c 3 2 W m 2 d 2 9 W m The al 10 5 t T The

Physics

Electromagnetic wavesSolveLancer Test The mathematical expression for Pointing Vector is given by S Ex B The term S x t always points in the Ho i Negative X direction ii Direction of wave propagation SolveLancer Test a Only i true b i ii both false c i ii both true d Only ii true