Electromagnetic waves Questions and Answers

Electrons used in an electron microscope are accelerated by a voltage of 25 kV If the voltage is increased to 100 kV then the de Broglie wavelength associated with the electrons would AIPMT Prelims 2011 1 Increase by 4 times 2 Increase by 2 times 3 Decrease by 2 times 4 Decrease by 4 times

Which of the following statement s regarding EM waves is are false a The ratio of electric field strength En to magnetic field strength Ho of a plane electromagnetic wave in vacuum has the dimensions of electric resistance and is always equal to one b The average value of electric field in a plane electromagnetic wave is independent of electric energy and has a constant non zero magnitude perpendicular to the direction of wave propagation c The frequency of oscillation of energy contained in a small volume through which an electromag netic wave is passing would be double the frequency of the wave d An electron released from rest in the path of a plane electromagnetic wave will start moving along the direction of wave propagation

ik 7 wt Assume E E where k 2 k cos ik sing k 1k and and 2 a Cartesian unit vectors Choose the correct statement a Electric field s magnitude is attenuated with the propagation of wave b The energy of the electromagnetic wave is flowing in the x direction c Electric field s magnitude is constant d Speed of wave is same as speed of light that is c

PLEASE EXPLAIN ALL OPTION HOW to know TYPE OF PO ARIZATION An electromognetic wave travels in vacuum along z direction E E i E j cos kz wt Choose the correct options from the following a The associated magnetic field is given B E E cos kz wt b The associated magnetic field is B E i E cos kz oot QU c The given electromagnetic field is circularly polarised d The given electromagnetic wave is plane polarised as as

A 60 kg model rocket lifts off by expelling fuel downward at a rate of k 4 75 kg s for 7 s The fuel leaves the end of the rocket with an exhaust velocity of b 100 m s Let m t be the mass of the rocket at time t From the law of conservation of momentum the following differential equation for the rocket s velocity u t in meters per second is obtained m t v t 9 8m t b dm 7 dt Compute the rocket s velocity at rocket burnout after 7 s Use decimal notation Give your answer to three decimal places m s

The region z 0 of a Cartesian coordinate system contains a linear isotropic dielectric of dielectric constant 2 0 The region z 0 is the free space A free space charge density of SnC m is at the interface z 0 If the displacement vector in the dielectric is D 3 4 6 nC m find the corresponding displacement vector D in the free space

What does the speed of light postulate state O a The speed of light in a vacuum is constant unless the viewer is moving toward or away from the light source b The speed of light in a vacuum has the same value in all directions and in all inertial reference frames OC The speed of light in a vacuum varies with the wavelength but is a constant for each wavelength in all reference frames Od The speed of light

Force experienced electromagnetic by a charged particle in an field is zero If the charge on the particle is q velocity of the particle is v and the electric and magnetic fields are and B respectively then which of the following is possible 0 B 0 v 0 q 0 0 B 0 v 0 q 0 0 B 0 v 0 q 0 All of these

When photons of energy 5 eV strike the surface of a metal A the ejected photoelectrons have maximum kinetic energy K eV and de Broglie wavelength The maximum kinetic energy of photoelectrons liberated from another metal B by photons of energy 5 30 eV is K K 1 5 eV If the de Broglie wavelength of these photoelectrons is g 22 then find K3 in eV I

magnetic field of a plane electromagnetic wave is B 3 108 sin 200m y ct iT where c 3 108 ms is the speed of light The corresponding electric field is 1 9sin 200n y ct k V m 2 E 106 sin 200m y ct k V m 3 E 3 108 sin 2007 y ct k V m 4 E 9 sin 200r v ct lk V m

A proton moves with a speed u directly toward a free proton originally at rest Find the distance of closest approach f the two protons Given that mass of the proton is m and charge of the proton is e

If a wire in the earth s magnetic field carries a current vertically downwards it is possible to obtain a neutral point 1 North of the wire 2 South of the wire 3 East of the wire

BPH2101 PHYSICS REMAINING TIME HOURS MINUTES SECONDS 1 46 5 46 Why is laser light monochromatic O Photons of the same energy as that of the incident photons are emitted when the electrons transit down from a higher energy level The system is in a state of population inversion A O The emitted photon and incident photon are of the sam phase The excited electrons are in a metastable state

BPH2101 PHYSICS REMAINING TIME HOURS MINUTES SECONDS 1 46 49 Which property of an electromagnetic wave depends on the medium in which it is travelling O Velocity O Frequency Owave length Time period

BPH2101 PHYSICS 43 If a material had a modulus of elasticity of 2 1 kgf cm2 and a modulus of rigidity of 0 8 kgf cm2 then what will be the approximate value of the REMAINING TIME HOURS MINUTES SECONDS 1 47 0 Poissons ratio 00 43 00 31 00 47 0 26

PH2101 PHYSICS REMAINING TIME HOURS MINUTES SECONDS 1 55 2 12 In an electromagnetic wave the electric field of amplitude 6 2 Vim oscillates with a frequency of 2 4 X 1010 Hz The Energy density of the war O4 4 x 10 101 m3 O14 X 10 10J m3 Oz4 x 10 101 m3 O3 4 X 10 101 m3

What happens by the use of white light in Young s double slit experiment 1 Bright fringes are obtained 2 Only bright and dark fringes are obtained 3 Central fringes is bright and two or three coloured and dark fringes are observed 4 None of the above

VO in a material medium when a positron meets an electron both the particles annihilate leading to the emission of two gamma ray photons This process forms the basis of an important diagnostic procedure called a MRI AIIMS 2003 c CAT 2H H b PET d SPECT 4 He mass of deuteron

field of an electromagnetic wave is given by E 50 N C sin o t x c the energy contained in a cylinder of cross section 10cm and length 50 cm along the x axis 1 5 5 10 J 2 5 5 10 2 J 3 2 75 10 J 4 2 75 10 2 J 700 1400x Brost to XX168 700 1400 to

Consider the following two statements Statement A In the wave picture of light intensity of light is determined by the square of the amplitude of the wave Statement B For a given frequency intensity of light in the photon picture is determined by the number of photons crossing a unit area per unit time Which of the following option is correct Statement A is correct while statement B is incorrect

Electromagnetic wave having magnetic field B x y z t B sin x y ot where k is wave vector Calculate its electric field a cB sin x y cx cot b cB sin x y 2 C CB sin x y 2 x 1 d cB sin x y cot 2

10 A material undergoes a magnetostructural transition at a temperature that depends linearly on the applied stress as 0 13 K MPa and also linearly on the dr dr magnetic field as HodH 2 1 KT If the transition involves a strain of 5 determine the magnetization change at the transition using the Clausius Clapeyron equations for both the magnetic and strain degrees of freedom

Applying the related fundamentals of electromagnetic wave propagation determine the shielding effectiveness in dB for a 0 508 mm thick sheet of copper o 5 8 x 107 S m at 1MHz given a An electric source at a distance 1 m from the shield b A magnetic source at a distance 1 m from the shield

BRB BB K B Re Voc the figure given that VBB supply can vary from 0 to 5 0 V Vcc 5V Bdc 200 B 100 kQ Rc 1k0 and VBE 1 0 V The minimum base current and the input voltage at which the ansistor will go to saturation will be respectively 20 A and 3 5V 25uA and 3 5V JEE Main 2019 Jan 3 25uA and 2 8V 4 20uA and 2 8V

field part of an electromagnetic wave in vacuum is rad E 6 cos 1 2 Y 3 6 108 rad S Ve Frequency of propagation Wavelength 2 then find c Direction of propagation Amplitude of magnetic field in electromagnetic wave An e ression for magnetic field part of the wave

11 10 pts A gate on a vertical dam is an isosceles triangle with base 4 meters wide located 2 meters above the water surface The vertex of the triangle is 2 meters below the water surface Find the force against the gate

A flat and homogeneous wave polarized in the x direction and having a frequency of 150 Mhz propagates in air from the negative z direction to the positive z direction This wave hits an ideal conducting plane which lies at z 0 If the amplitude of the electric field is 12 mV m Calculate The phasor shape and time function of the reflected electric and magnetic fields

Q 9 A quarter wave plate is placed in between a polarizer and a photo director When the optic axis of the quarter wave plate is kept initially parallel to the pass axis of the polarizer and perpendicular to the direction of light propagation The intensity of light passing through the quarter wave plate is measured to be Io see figure If the quarter wave plate is now rotated by 45 about an axis parallel to the light propagation what would be the intensity of the emergent light measured by the photo director

Cons figure q x a x a Variation of electric field along x axis is 1 2 3 q charge conti a x 0 x 0 ai a

The voltage time graph for triangular wave having peak value Vo is shown in figure If V and V be the average and rms voltage for the time interval 0 to respectively then VA V 712 T V 2V 3 V V 2 374 t T 1712

46 If a star emitting light of wavelength 500 nm is moving towards earth with a velocity of 1 5 x 106 m s then the shift in the wavelength due to doppler s effect will be 1 25 A 3 2 5 A 2 250 A 4 Zero

An EM wave with a maximum electric field of 20V illuminates a surface with an area of 0 50ms The EM wave is incident on the surface at an angle of 37 to the surface normal Compute the force on this surface if the wave is reflected completely

Four electric charges A B C D are arranged as shown The electric force will be least between charges A B 2 C 4 C D a A and B c B and D O a O b O c d 4 C 2 C b A and D d A and C C

When plane polarized light having plane of incident as plane of vibration is incident at Brewster s angle A B reflected light will be polarised There will be no reflection there will be no refraction none of the above

29 A beam of plane polarised light of large cross sectional area and uniform intensit of 3 3Wm2 falls normally on a polariser cross sectional area 3 x 10 m whic rotates about its axis with an angular speed of 31 trad s The energy of light pass ing through the polariser per revolution is close to A 1 0 10 J B 5 0 10 J C 1 0x 10 5 J D 1 5x10 J

Q4 The electric field intensity produced by the radiations coming from 100 W bulb at a 3 m distance is E The electric field intensity produced by the radiations coming from 50 W bulb at the same distance is 6 2E c d 2E 61 From NC D

Q8 Figure shows a parallel plate capacitor being charged by a battery If X and Y are two closed curves then during charging B di is zero along the curve f104 1 X only 2 Y only 3 Both X Y 4 Neither X nor Y

Choose the correct option relating wavelengths of different parts of electromagnet wave spectrum A Aradio waves Amicro Avisible Ar rays waves B Avisible Amicro waves Aratio waves Ar rays C Avisible Ar rays Aradio Amicro waves D Ar Tous Amicrowaves Aradio waves Avisible waves

A plane electromagnetic wave is given by Eo exp i kz wt At a given location the numb times E vanishes in one second is a An integer near when n and zero when nr nis integer b An integer near c An integer near T d An integer near 0 T 3 5 and is independent of 8 2 when 8 n and zero when nr n is integer and is independent of 8

The next values are given for electric and magnetic field at a certain moment and in a certain environment E 80 0i 32 0j 64 ok N C and B 0 2001 0 0800j 0 290k HT Those two fields belong to the same electromagnetic wave Find the Poynting vector of this wave Give the final answer only with three significant figures

A plane electromagnetic wave of frequency of 50 MHz travel in free space along x axis At a particular point in space and time amplitude of electric field vectors is E 9 3 V m What is amplitude of magnetic field vector at that point 3 1x 10 8 T 3 1 10 7 ki 9 3x10 8 KT 3 1x10 8 KT

5 The magnetic field in plane electromagnetic wave is given by 4 x 10 6 sin 0 2 x 104x 0 6 x 1012 t T then find By a Frequency b Wavelength c Speed of the wave d Expression for electric field part of the electromagnetic wave

A steel ball bearing with a 12mm diameter is heated in boiling water for 10 minutes and then placed in an insulated cup filled with cold water at 5 degrees Celsius What is the final of the ball and water at temperature equilibrium

ky cos 8 Which one of the following is INCORRECT statement in the transmission of electromagnetic waves Kerala PET 201 a Ground wave propagation is for high frequency transmission b Sky wave propagation is facilitated by ionospheric layers c Space wave is of high frequency and is suitable for line of sight communication d Space wave is used for satellite communication e Very high frequency waves cannot be reflected by the ionospheric layers axis is 934 m The a 3 1x10 T c 3x10 T What does the poynting vector represent J K CET 2012 across unit area in an electromagnetic field 47 Which one monochro e 3 1x10 in an a Ele b

Kegaraing nature of electromagnetic waves incorrect statement is Electric and magnetic fields in electromagnetic wave are perpendicular to each other Electric field and magnetic field are to direction of perpendicular propagation of electromagnetic wave Electromagnetic waves has self sustaining oscillations of electric and magnetic field in vacuum The velocity of electromagnetic wave is

Electromagnetic waves referred as heat waves are Visible light rays O Microwaves Infrared waves X rays

The correct order of decreasing frequency of electromagnetic waves is sec X rays infrared ultraviolet microwaves X rays ultraviolet infrared microwaves Microwaves ultraviolet infrared X rays Ultraviolet X rays infrared microwaves

Which wave in the electromagnetic spectrum has the following properties A Wavelength ranges from 0 6 nm to 400 nm B It causes tanning of skin C It is absorbed by ozone layer O Ultraviolet rays X rays Gamma rays Infrared rays

The frequency of electromagnetic wave is Equal to frequency of oscillation of charge producing the wave Double to frequency of oscillation of charge producing the wave Half of frequency of oscillation of charge producing the wave Independent of frequency of oscillation of charge producing the wave

Which among the following is not an electromagnetic wave X rays y rays B rays O Visible light mi