Electromagnetic waves Questions and Answers

3 1 2 Which of the following combination of E and B is possible if a charged particle passes undeviated from a region 1 E 0 B 0 3 B 0 E 0 A wire of length 2 m is placed in uniform magnetic field of tesla It makes 30 with the field If 10 A 2 E 0 B 0 4 All of these

Q 2 If an average person jogs he produces 14 5x 10 cal min This is removed by the evaporation of sweat The amount of sweat evaporated per minute assuming 1 kg requires 580 10 cal for evaporation is d 0 20 kg a 0 25 kg b 2 25 kg c 0 05 kg d minuto

6 Electrostatic force between two small spheres at separation r is F Now both spheres are touched and again placed at separation r then electrostatic force between them becomes their initial charges is 1 3 4 2 2 1 3 9F 8 35 Then ratio of 4

A wooden block of mass 100 kg is kept on a horizontal platform A force of 60 N is required to just slide the block But a force of 49 N is just sufficient to keep the block moving with uniform velocity What is the coefficient of kinetic friction a 0 5 c 0 05 b 0 25 d 0 005

A plane E M wave propagating in x direction has wavelength 10 mm electric field in the y direction and its maximum magnitude is 30 Write suitable equation for magnetic field as a function of x and t Wave is in vacuum m By 10 7 sin 6 10 0 t 200 x Bx 10 7 sin 6 10 0 t 200 x B 30 sin 6 10 0 t 200 x B 10 7 sin 6 10 t 200 x

Consider the volume of space bounded by the capacitor plates blue region Compute the Poynting vector at the outside cylindrical surface of that volume Which way does it point A Parallel to the surface from left to right B Parallel to the surface from right to left C Inward to the surface D Outward to the surface E Azimuthally parallel to the surface R S

3 In a lossless nonmagnetic material with Determine Er 16 and H 50 cos t 20x j mA m i The propagation velocity ii The angular frequency iii The instantaneous expression for the electric field intensity 4 A plane wave travelling in a medium of 0 5 0 5 has an ele of 100 V m Determine the energy density in the magnetic field energy density at alat alat

An X ray has a wavelength of 0 010 Its momentum is AFMC 1980 RPMT 1995 Pb PMT 2004 RPMT 2005 b 6 626x10 22 kg m s a 2 126x10 23 kg m s c 3 456x20 25 kg m s d 3 313x10 22 kg m s th

A positive point charge q is placed at a distance 2R from the surface of a metallic shell of radius R The electric field at centre of shell due to induced charge has magnitude 1 Zero 1 O q 2R 2209 q 1 2 4 9R 1 q

13 Two particles execute SHM of same amplitude of 20 cm with same period along the same line about the same equilibrium position The maximum distance between the two is 20 cm Their phase difference in radius is 1 2 3 2 17 12 A plank with a small block EN 3 TU 3 4 TC

In amplitude modulation sinusoidal carrier frequency used is denoted by c and the signal frequency is denoted by m The bandwidth Aom of the signal is such that Am c Which of the following frequencies is not contained in the modulated wave 2017 1 c m 3 Oc 2 m 4 m c

158 The ratio of contributions made by the electric field and magnetic field components to the intensity of an electromagnetic wave is c speed of electromagnetic waves c 1 1 1 1 c 4 1 c 1 2 FE Fo C T puen

After undergoing through 90 Compton scattering the fraction of energy lost by photon is A 50 B 10 zero D None of above m bz

In an electromagnetic wave travelling in free space the rms value of the electric field is 3 V m The peak value of the magnetic field is a 1 414 x 10 T c 2 828 x 10 T b 1 0 10 T d 2 0 x 10 T

The Lagrangian of a system with one degree of freedom q is given by L q Bq where a and are non zero constants If pq denotes the canonical mom then which one of the following statement is CORRECT a pq 2 q and it is a conserved quantity Pq 33 b pq 23q and it is not a conserved quantity Pq 2aq and it is a conserved quantity c Pq

20 In EM wave which of following vector is responsible 4 for optical effects 1 E 3 Poynting vector 2 B 4 Velocity

For a new unit of length the speed of radio waves is unity Find the distance of an aircraft from a RADAR if the radio signal returns back after reflection from Ans 4 2 x 106 new unit the aircraft in 8 4 s

A body of mass 2 kg and density 2 7 g cm 3 is sus pended by a steel wire of length 1 m and radius 1 mm If the body is completely immersed in water what will be the change in length of the wire Y of steel 2 x 10 2 dyn cm 2 and g 980 cm s 1 15 x 10 3 cm

Illustration 1 The magnetic field in a plane em wave is given by By 2x 10 7 sin 3 14 x 103 x 6 28 x 1011 t T i what is the wavelength and frequency of the wave ii write an expression for the electric field

A conducting rod PQ of length L 1 0 m is moving with a uniform speed v 2 0 m s in a uniform magnetic field B 4 0 T directed into the paper A capacitor of capacity C 10 F is connected as shown in figure Then X A B X X X a X V X 1 A 80 C and q 80 C 2 A 80 C and q 80 C 3 A 0 9B 4 charge stored in the capacitor increases

12 For radioactive decay AN At At N nuclei not decayed Half life T1 2 0 693 A A decay constant 13 1 u of mass 931 5 MeV of energy Question 1 equivalence 1 unit converts to 931 5 MeV c OV EoHo K Ov 1 K EoHo Ov 1 K EoHo 1 pt Theoretically the speed of light c through vacuum is expressed as c 1 EH E and o are the electric permittivity and magnetic permeability of free space vacuum Therefore for a medium with dielectric constant x the speed of light v should be expressed as

12 Which of the following statements are true Select all that apply Photons have mass The energy of a photon increases as frequency increases The energy of a photon is directly proportional to the photon s frequency Photons only have kinetic energy

14 What is the de Broglie wavelength of a 2 67 x 10 24 kg particle moving at 3 19 x 106 m s h 6 626 x 1034 J s 5 55 x 10 17 m 7 78 x 10 17 m 9 16 x 10 17 m 3 48 x 10 17 m

Mrs Spencer took out a loan to pay for a car She was required to pay 12 25 interest compounded monthly on the unpaid balance of her loan She borrowed 20 000 and made no payments for five years How much did she owe at the end of five years with interest added 6 Points Show your work

What has the highest frequency 1 gamma ray 2 radio wave 3 infrared light 4 visible light 5 X ray

a When an object is charged by conduction the charging object and the electroscope end up with b When an object is charged by induction the charging object and the electroscope end up with c When an object is charged by polarization the leaves and the knob of the electroscope end up with charges charges charges

VP 23 3 1 Part A A sinusoidal electromagnetic wave is traveling in the z direction It has a period of 2 us and its magnetic field magnitude is 1 x 10 2 T Write down the equation for the magnitude of the wave s electric field vector E Express your answer in volts per meter in terms of t 7 and z Express the coefficients using three signature figures VAE xa Xb 26 x x x x IXI X 10n X

When radio waves are compared with visible light both have the same wavelength O both travel at the same speed both have the same frequency visible light travels faster than radio

3 20 points a 10 points Calculate the squared error distortion for the following Data and Centers Data 2 8 2 5 6 9 7 5 5 2 Centers 3 5 5 4 b 10 points Explain why the Lloyd algorithm must converge

a Rank the parts of the electromagnetic spectrum from lowest frequency a to highest g b What is the relationship between frequency and wavelength

A typical hair dryer uses 1850J every second How much matter would have to be converted to energy every second to keep the hair dryer going 6 17x1066kg 2 06x10 14kg 6 17x10 6kg 1 67x1020 kg

All electromagnetic waves move at the speed of light Select one True O False

The U S Army s loudest loudspeaker is almost 17m across and is transported on a special trailer The sound is produced by an electromagnetic coil that can generate a minimum frequency of 10Hz what is the wavelength of these electromagnetic waves Select one a 3x105 km O b 3x107 m O c 3x104 m O d 3x107 km

Commercial trucks cause about 18 000 lane change and merging accidents per year in the United States To prevent many of them a warning system covering blind spots is being developed The system uses electromagnetic waves of frequency 2 4x10 0Hz What is the wavelength of these waves

The highest directly measured frequency is 5 2x1014Hz corresponding to one of the transitions in iodine 127 How many wavelengths of electromagnetic waves with this frequency could fit across a dot on a book page Assume the dot is 2x104m in diameter

Cordless phones use a 800x106Hz frequency and can be operated up to 60m from their base What is the wavelength of these waves Select one a 1m b 375m O c 3x10 m O d 24 x 1018

You measure the rest wavelength in the lab of a spectral line to be 450 nm You identify that same line in 3 different stars Which of the following measured wavelengths corresponds to a star that is moving away from us Select one A 464 nm OB 450 nm C 441 nm

Problem 1 In class we considered a plane parallel sinusoidal wave of the form E Eo cos kz wt B Boy cos kz wt where Eo and Bo are amplitudes k is the magnitude of a wave number and w is an angular frequency The y component of the Maxwell s equation involving VX E in vacuum is d dz and the component of the equation involving V x B is d d dy dz d B B Hofo Ez dt Ex d Ez dx d dt 1 2 By 3 4 Show by taking the derivatives and plugging in that the given forms for the electric and magnetic fields can satisfy these equations provided that there is some particular relationship between Eo and Bo and some particular relationship between k and w What are those relationships You should be able to write an expression for the ratio Eo Bo and an expression for the ratio w k Both of these expressions should depend only on fundamental constants w Fo and C

Consider a gas of hydrogenic single electron atoms which are described by the energy level diagram shown at right These atoms are all initially in their ground state and have very short lifetimes that is an excited atom will completely relax before it can be excited again a You shine white light onto a gas of these atoms What colors wavelengths of light will be absorbed Show your work and explain your reasoning 0 eV E 3 eV E 5 eV E 10 eV b Will the number of unique colors wavelengths emitted by the gas be greater than less than or equal to the number of colors absorbed by the gas Explain your reasoning

from 4 to 2 from 1 to 3 An electron absorbs 23 eV of energy What transition does the electron make Ofrom 2 to 4 7 65 eV 13 6 eV from 3 to 1 30 6 eV 122 4 eV n 5 n 4 n 3 n 2 n 1 1 of 10 NEXT

redshift Electromagnetic Spectrum astronomical unit

Ovide an example of a use for ultrasonic waves

Your radio is tuned to 103 5 on the FM dial a What electromagnetic wave frequency is your radio receiving b How fast is this wave traveling c What is the wavelength

Why do you think the discovery of radio waves and of X rays are covered in this chapter that focuses on light a Visible light is really a low frequency radio wave b Radio waves and X rays are a form of light Oc Most radio waves and X rays are visible when viewed in a vacuum d Like radio waves and X rays visible light is a form of electromagnetic wave

hat can you conclude comparing the speed of wave at frequency of G and that of the 3rd harmonic O The speed of wave decreases with the harmonic number O The speed of wave is the same for all harmonics in the same string You cannot change the speed of wave in a string The speed of wave increases with the harmonic number

The frequency of this c m 10 9 m 1 nm Submit Answer

Question 10 How are EM waves different O EM and sound waves are the

What would be the approximate speed of an EM wave expressed in terms of the unit of Earth's circumference (4.01 x 10^7 m). A. 5 units B. 10 units C. 13 units D. 7.5 units

Consider a plane electromagnetic wave that is traveling vertically downward with its electric field pointing East-West. In what direction(s) does the magnetic field point? A. East-West B. Magnetic field not predictable C. Up-down D. North-South

Arranging electromagnetic (EM) waves in an order of lower to higher frequencies may categorize these rays as below: A. Radio waves, infra red waves, visible waves, ultraviolet waves, X-ray waves, gamma ray waves B. Radio waves, infra red waves, ultraviolet waves, visible waves, X-ray waves, gamma ray waves C. Radio waves, infra red waves, ultraviolet waves, visible waves, X-ray waves, gamma- ray waves D. Infra red waves, radio visible waves, ultraviolet waves, gamma-ray waves, X-ray waves