# Electromagnetic waves Questions and Answers

Physics
Electromagnetic waves
A cell can be balanced against 110 cm and 100 cm of potentiometer wire respectively with and without being short circuited through a resistance of 10 Q2 Its internal resistance is a 2 0 ohm c 1 0 ohm b zero d 0 5 ohm
Physics
Electromagnetic waves
If an electrion is placed in a uniform electric field then the electron will 1 experience no force 2 moving with constant velocity in the direction of the filed 3 move with constant velocity in the direction opposite to the field 4 accelerate in direction opposite to field
Physics
Electromagnetic waves
6 In the EM wave the amplitude of magnetising field H and the amplitude of electric field E at any place are related as 1 H Eo 3 H Eo Ho 2 Ho E C 4 H E Eo
Physics
Electromagnetic waves
3 0 3 If and E are current density and electric field respectively inside a current carrying conductor then corred relation is 1 GE 3 j 0 2 jxE 0 4 All of these
Physics
Electromagnetic waves
The condition under which a microwave oven heats up a food item containing water molecules most efficiently is The frequency of the microwaves has no relation with natural frequency of water molecules Microwaves are heat waves so always produce heating Infrared waves produce heating in a microwave oven The frequency of the microwaves must match the resonant frequency of the water molecules
Physics
Electromagnetic waves
12 A parallel plate capacitor with ci radius a is being charged as shown in the figure At the instant shown the displacement current in the to region between the plates enclosed between a is given by Id 000 2 1 i 3 8 8 4 100 TO 9 3 POIA
Physics
Electromagnetic waves
Two circular plates of radius 0 2 m are used to form a parallel plate capacitor displacement current between the plates is ampere then the magnetic field produced by displacement current at 0 1 m from the axis of the plate will be 5 x 10 7 T 4 x 10 7 T 5 x 10 6 T axis of the plate
Physics
Electromagnetic waves
Which of the following is true 1 Lyman series is a continuous spectrum 2 Paschen series is a line spectrum in the infrared c 3 Balmer series is a line spectrum in the ultraviolet 4 The spectral series formula can be derived from the Rutherford model of the hydrogen atom
Physics
Electromagnetic waves
Light with intensity 18 W cm falls on non reflecting surface at normal incidence If surface has an area of 20 cm2 find the average power exertec surface during time span of one minute 0 1 2 x 10 6 N 2 4 x 10 6 N 3 2 x 10 6 N 1 9 10 5 N
Physics
Electromagnetic waves
1 2eV m 2 2eV m the The 21 cm radio wave emitted by hydrogen in interstellar space is due to ter interaction called teh hyperfine interaction natomic hydrogen The energy of the emitted wave is nearly 1 10 7 J 2 IJ 3 7 10 J 4 10 J U Rohr s model of a hydrogen atom the enctripetal force is furnished by the Coulomb attraction between te rhit mis the mass and e is the charge on the electre
Physics
Electromagnetic waves
31 In Negative crystal velocity of 1 Point Velocity of O ray is greater than Velocity of E ray in all directions except along optic axis Velocity of 0 ray is less than Velocity of E ray in all directions except along optic axis O ray E ray is equal in all directions except along optic axis
Physics
Electromagnetic waves
OR Write the expression for speed of electromagnetic waves in a medium of electr permittivity and magnetic permeability u 22 An a particle and a proton are accelerated th
Physics
Electromagnetic waves
Figure shows an irregular shaped with AB moving with velocity v as shown Find the emf induced in the wire OB B
Physics
Electromagnetic waves
The electric field of a plane electromagnetic wave in vaccum is represented by Ex 0 Ey 0 5 cos quantities are is S I units Find the component of magnetic field associated with the wave os 2 108 t 1 tesla X O 0 17 10 cos 27 x 10 t a tesla O 0 17 x 10 8 sin 2 x 108 t 1 tes O 0 15 x 10 cos O 0 15 x 10 sin 2 tesla x 108 t 1 tesla cos 27 x 108 t 1 with C 3 108 m sec E 0 all 4
Physics
Electromagnetic waves
Four resistances are connected by an ideal battery of emf 50 volt circuit is in steady state then the current in wire AB is 1 12 192 www www 302 A B 202 www 3 402 57 X Vp 312 412 413 50 6i3 413 5 1013 St 3x3 13
Physics
Electromagnetic waves
A car is traveling 32 m s down a level road where Earth s magnetic field 5 0 x 10 5 T points north with an angle of 38 What is the maximum induced emf by the car s 63 cm antenna 6 01 x 10 4 V 5 50 x 10 4 V 7 94 x 10 4 V 5 75 x 10 4 V
Physics
Electromagnetic waves
3 The maximum electric field at a distance of 10 m from an isotropic point source of light is 3 0 Vm Calculate a the maximum value of magnetic field b average intensity of the light at that place and c the power of the source
Physics
Electromagnetic waves
An electromagnetic wave is represented by the electric field E Ensin oot 6y 8z Taking unit vectors in x y and z directions to be i j k the direction of propagation is S A B C D S 3j 4k 5 31 4 5 4k 3j 5 4j 3k 5 4 YOU MARKED
Physics
Electromagnetic waves
In a bicycle speedometer a attached to the spokes of the wheel and a coil is attached to the frame so that the north pole of the magnet moves past it once for every revolution of the wheel As the magnet moves past the coil a pulse of current is induced in the coil A computer then measures the time between pulses and computes the bicycle s speed Figure shows the magnet about to move past the coil Which of the graphs shows the resulting current pulse Take counterclockwise in figure current to be positive Magnet north pole facing the viewer Plane of Coil is nearer to you 1 v A A N 4 3 2
Physics
Electromagnetic waves
9 An electron beam has the diameter 1 mm the electrons have the kinetic energy T 10keV What is the charge density in the beam if the total current is 2 10 A 10 The mobility of electrons u in a conductor is defined by the equation vdrift E Find an expression
Physics
Electromagnetic waves
56 The average electric field of electromagnetic waves in certain region of free space is 9 x 104 N C Then average magnetic field in same region is 1 27 x 104 T x 10 2 3 2 3 x 10 2 4 3 x 10 2
Physics
Electromagnetic waves
Force experienced by a charged particle in an electromagnetic field is zero If the charge on the particle is q velocity of the particle is and the electric and magnetic fields are E and B respectively then which of the following is possible OE 0 B 0 0 9 0 O E 0 B 0 0 90 OE 0 B 0 0 q 0 All of these
Physics
Electromagnetic waves
The displacement of the wave given equation y x t asin kx ot wh p 0 at point x and t 0 is same as that at poi 1 x 2n 3 kx 2n 2 x 2nt k 4 None
Physics
Electromagnetic waves
An air mass at 100 relatively humidity is forced up and over a mountain range At the peak of the mountain range immediately before it starts to descend down the other side it reaches a temperature of 2 degrees Celsius Calculate the temperature of the air mass after it has descended 360 m down the other side of the mountain range L r
Physics
Electromagnetic waves
CAREER ENDEAVOUR Problem Consider a two dimensional hexagonal lattice if lattice spacing a 3 and sound velocity c 10m sec The debye frequency w is provide a humerical value in sec D a 1 1x10 3 b 2 2 10 5 c 0 6 10 3 d 1016 S 2
Physics
Electromagnetic waves
114 An electromagnetic wave is travelling in a medium of permeability and permittivity e If e is speed of the wave in free space then the refractive index of the medium is a as Dagdas bordad son riso pardo e do o y no 040 38955 Momso C 11 3 no cod rito ant 4
Physics
Electromagnetic waves
L ms in the plane of the table collide with the two ends of the rod simultaneously as shown in the figure The marbles stuck to the rod and continue to move with the rod Time taken by the rod to rotate through an angle radian is in seconds M agos L sne a Deo 55 0 55rodowy 56 M 6 de L ms 2560 586 od r5 Doom s dod 550 650 v sznon sjetin sadjon I d ng s min ahmo domnum s e sus SO 0 Options 1 1 2 2 T od do 1050 206 157 5 por ter od Jora New 3 T Rod 5
Physics
Electromagnetic waves
choose the one that best describes the two statements Statements 1 Out of the radio waves and microwaves the radio waves undergo more diffraction Statement 2 Radio waves have greater frequency compared to microwaves A Statement 1 is true Statement 2 is true Statement 2 is the correct explanation of Statement 1 B Statement 1 is false Statement 2 is true C Statement 1 is true Statement 2 is false D Statement 1 is true Statement 2 is true Statement 2 is not the correct explanation of 2013 Statement 1
Physics
Electromagnetic waves
A plane electromagnetic wave in a non magnetic dielectric medium is given by E E 4 10 7x 50t with distance being in meter and time in seconds The dielectric constant of the medium is A 2 4 2013 C 8 2 B 5 8 D 4 8
Physics
Electromagnetic waves
A plane electromagnetic wave of frequency 100MHz is travelling in vacuum along the x direction At a particular point in space and time B 2 0 10 T where k is unit vector along z direction What is E at this point 1 0 6 V m 2 6 0kV m 3 6 0 V m 4 0 6kV m
Physics
Electromagnetic waves
o Bok 4 E B K 35 Relation between electric field and magnet field in electromagnetic wave is ECB wher c speed of light in vacuum Ratio of energ density in electric to the magnetic fields is 1 c 1 3 C 1 2 1 c 4 1 1
Physics
Electromagnetic waves
The correct sequence of the increasing wavelength of the given radiation sources is a radioactive sources X rays tube crystal oscillator sodium vapour lamp aves b radioactive source X rays tube sodium vapour lamp crystal oscillator c X ray tube radioactive source crystal oscillator sodium vapour lamp d X rays tube crystal oscillator radioactive omn
Physics
Electromagnetic waves
Assertion The specific charge for positive rays is a characteristic constant Reason The specific charge depends on charge and mass of positive ions present in positive rays 1 If both the assertion and the reason are true and the reason is a correct explanation of the assertion 2 If both the assertion and reason are true but the reason is not a correct explanation of the assertion 3 If the assertion is true but the reason is false 4 If both the assertion and reason are false
Physics
Electromagnetic waves
The magnetic field of a plane electromagnetic wave is B 3 108 sin 2007 y ct i T where c 3 108 ms 1 is the speed of light The corresponding electric field is A E BE E C 10 6 sin 2007 y ct k V m 9 sin 2007 y ct V m E 9 sin 2007 y ct V m
Physics
Electromagnetic waves
c 740 J d 2 enters in a An electromagnetic wave of intensity 50Wm medium of refractive index n without any loss The ratio of the magnitudes of electric fields and the ratio of the magnitudes of magnetic fields of the wave before and after entering into the medium are respectively given by JEE Main 2019 a n n n n b n n J d 15 5 ids of same length 1 The
Physics
Electromagnetic waves
A 100 ohm resistor is connected in series with a 4 H inductor The voltage across resistor is Vo 2 sin 1900 The voltage across inductor is 1 60 sm 1000 t x 2 2 8 sin 1000 2 3 80 sin 1000 2 4 6 sin 1000 t 2
Physics
Electromagnetic waves
Positive rays travelling from west to east enter in a region of electric field directed vertically upwards The deflection of the rays is towards Neglect effect of gravity 1 Vertically upwards 2 Vertically downwards 3 North 4 South
Physics
Electromagnetic waves
A mono chromatic source emits parallel beam of light of power 60 W emits 10 8 photons s All these photons falls normally on a black surface and get absorbed The momentum of each photon and the force exerted by these photons on the surface respectively in S I units are
Physics
Electromagnetic waves
Electromagnetic radiations of intensity 1 W m strikes on the surface of a substance which reflect 80 incident radiation back into same medium The radiation pressure on the surface of substance is Only one correct answer A 4 10 8 N m B 2 5 10 7 N m C D 8 10 8 N m 6x 10 9 N m i
Physics
Electromagnetic waves
Consider the four statements given below about the function f x x x in the range x o Which one of the following statements is correct P the plot of f x versus x has two maxima and two minima Q the plot of f x versus x cuts the x axis at four points R the plot of f x versus x has three extrema S no part of the plot f x versus x lies in the fourth quadrant Pick the right combination of correct choices from those given below a P and R b R only c R and S d P and Q
Physics
Electromagnetic waves
Given a wave with the dispersion relation w ck m for k 0 and m 0 which one of the following is true a The group velocity is greater than the phase velocity b The group velocity is less than the phase velocity c The group velocity and the phase velocity are equal d There is no definite relation between the groun velocity and the pho
Physics
Electromagnetic waves
An electromagnetic wave is propagating in free space in the z direction If the electric field is given by E cos t kz i where oot ck then the magnetic field is given by a B 1 c cos t kz j b B 1 c sin wt kz j c B 1 c cos t kz i d B 1 c cos t kz j
Physics
Electromagnetic waves
20 The plates of a parallel plate capacitor are 4 cm apart the first plate is at 300 V and the second plate at 100 V The voltage at 3 cm from the second plate is b 400 V a 200 V c 250 V d 500 V 1 The potential of a charged spherical conductor of radius ris 10 Y The 1
Physics
Electromagnetic waves
41 An A C source is connected to a resistive circuit Which of the following statements is true A Current leads the voltage in phase B Current lags the voltage in phase C Current and voltage are in same phase D Either A or B depending on the value of resistance
Physics
Electromagnetic waves
please Solve and show Why and how poynting vector is v rying with time What realation is obtained How to get t he graph SOURCE NCERT EXEMPLAR 8 19 Poynting vectors S is defined as a vector whose magnitude is equal to the wave intensity and whose direction is along the direction of wave propogation Mathematically it is given by S ExB Show the nature of S vs t graph Ho
Physics
Electromagnetic waves
The electric and the magnetic field associated with an e m wave propagating along the z axis can be represented by 1 E Eoi B Boj 2 E Eok B Boi 3 E Eoj B Boi 4 E Eoj B Bok
Physics
Electromagnetic waves
For an electromagnetic wave propagating through vacuum the amplitude of electric field vector is 30 V m The maximum value of magnetic field is Only one correct answer A 2 8 T B C 3 T 0 1 UT i
Physics
Electromagnetic waves
Electromagnetic waves travel in a medium which has relative permeability 1 3 and relative permittivity 2 14 Speed of electromagnetic waves in this medium will be O 13 60 x 106 m s O 1 8 x 106 m s O 3 6 x 108 m s O 1 8 x 108 m s
Physics
Electromagnetic waves
In a plane electromagnetic wave the electric field oscillates sinusoid at a frequency of 2 0 x 1010 Hz and amplitude 48 V m 1 The wavele of the wave in vacuum is 0 1 5 m O 1 5 10 1 m 01 5 10 2 m 01 5 10 m
Physics
Electromagnetic waves
What type of ecological pyramid would be obtained with the following data NEET 2018 Secondary consumer 120 g Primary consumer 60 g Primary producer 10 g 1 Inverted pyramid of biomass 2 Pyramid of energy 3 Upright pyramid of biomass 4 Upright pyramid of numbers