Electromagnetic Waves PYQs Set 8 (PDF)

Set 8 of 9 · Questions 211-240 of 253

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Mere Teacher · Previous Year Questions JEE Main Physics · Electromagnetic Waves · Set 8 (Q211-240)
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211. $A charged particle with a velocity 2 \times 1 0^{3} m s^{- 1} passes undeflected through electric field and magnetic fields in mutually perpendicular directions. The magnetic field is 1.5 T . The magnitude of electric field will be$ (1) $1.5 \times 10^{3} N C^{- 1}$ (2) $2 \times 10^{3} NC^{- 1}$ (3) $3 \times 10^{3} NC^{- 1}$ (4) $1.33 \times 10^{3} NC^{- 1}$ 212. $The ratio of the magnitudes of electric field to the magnetic field of an electromagnetic wave is of the order of$ (1) $10^{- 8} m s^{- 1}$ (2) $10^{5} m s^{- 1}$ (3) $10^{- 5} m s^{- 1}$ (4) $1 0^{8} m s^{- 1}$ 213. $The maximum frequency of transmitted radio waves above which the radio waves are no longer reflected back by ionosphere is (N = maximum electron density of ionosphere, g = acceleration due to gravity)$ (1) $gN$ (2) $g N^{2}$ (3) $g N$ (4) $g^{2} N^{2}$ 214. $In the following List I consists of wave-length range of different of EM waves and List II consists of ways to produce them. Match the following Lists. List I A. 400 nm to 1 nm B. > 0.1 nm C. 1 mm to 700 nm D. < 10^{- 3} nm List II 1. Radioactive decay of the nucleus. 2. Vibration of atoms and molecules. 3: Rapid acceleration and deceleration of electron in aerials. 4. Inner shell electrons in atoms moving from one energy level to a lower level A B C D$ (1) $3 2 1 4$ (2) $2 3 4 1$ (3) $4 3 2 1$ (4) $1 4 3 2$ 215. $The electric field of an electromagnetic wave in free space is given by E = 10 cos (1 0^{7} t + kx) j V / m where t and x are in seconds and metres respectively. It can be inferred that (1) the wavelength λ is 188.4 m . (2) the wave number k is 0.33 rad / m . (3) the wave amplitude is 10 V / m . (4) the wave is propagating along + x direction. Which one of the following pairs of statements is correct?$ (1) $(3) and (4)$ (2) $(1) and (2)$ (3) $(2) and (3)$ (4) $(1) and (3)$ 216. $In amplitude modulation$ (1) $amplitude remains constant, but frequency changes.$ (2) $both amplitude and frequency do not change.$ (3) $both amplitude and frequency change.$ (4) $amplitude of the carrier wave changes according to information signal.$ 217. $What is the cause of Greenhouse effect?$ (1) $infra‐red rays$ (2) $ultraviolet rays$ (3) $X ‐rays$ (4) $radio waves$ 218. $Which of the following is/are the property/properties of a monochromatic electromagnetic wave propagating in the free space? 1. Electric and magnetic fields will have a phase difference \frac{π}{2} . 2. The energy of the wave is distributed equally between electric and magnetic fields. 3. The pressure exerted by the wave is the product of its speed and energy density. 4. The speed of the wave is equal to the ratio of the magnetic field to the electric field.$ (1) $1 and 3$ (2) $Only 2$ (3) $2 and 3$ (4) $Only 4$ 219. $Match List - I with List - II. List - I Relation (A) \oint E \cdot dl = - \frac{d}{dt} \oint B \cdot da (B) \oint B \cdot dl = μ_{0} (I + ϵ_{0} \frac{d φ _{E}}{dt}) (C) \oint E \cdot da = \frac{1}{ϵ _{0}} \int_{V} ρ d v (D) \oint B \cdot dl = μ_{0} I List - II Law (I) Ampere’s circuital law (II) Faraday’s laws of electromagnetic induction (III) Ampere - Maxwell law (IV) Gauss’s law of electrostatics Choose the correct answer from the options given below :$ (1) $A-II, B-III, C-I, D-IV$ (2) $A-II, B-III, C-IV, D-I$ (3) $A-I, B-IV, C-III, D-II$ (4) $A-IV, B-I, C-II, D-III$ 220. $Microwaves are used in$ (1) $TV$ (2) $radio transmission$ (3) $Radar$ (4) $atmospheric research$ 221. $The magnetic field in a travelling electromagnetic wave has a peak value of 20 nT. The peak value of electric field strength is :$ (1) $3 V/m$ (2) $6 V/m$ (3) $9 V/m$ (4) $12 V/m$ 222. $For an EM wave, the electric and magnetic fields are 300 V / m and 7.9 A / m, respectively. The maximum rate of energy flow is$ (1) $2730 \frac{W}{m ^{2}}$ (2) $2790 \frac{W}{m ^{2}}$ (3) $2370 \frac{W}{m ^{2}}$ (4) $2390 \frac{W}{m ^{2}}$ 223. $In an electromagnetic wave the electric field vector and magnetic field vector are given as E = E_{0} i and B = B_{0} k respectively. The direction of propagation of electromagnetic wave is along:$ (1) $(k)$ (2) $(j)$ (3) $(- k)$ (4) $(- j)$ 224. $Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Electromagnetic waves carry energy but not momentum. Reason (R): Mass of a photon is zero. choose the most appropriate answer from the options given below:$ (1) $Both (A) and (R) are true and (R) is the correct explanation of (A)$ (2) $Both (A) and (R) are true but (R) is not the correct explanation of (A)$ (3) $(A) is false but (R) is true$ (4) $(A) is true but (R) is false$ 225. $Arrange the following in the ascending order of wavelength: A. Gamma rays (λ_{1}) B. x - rays (λ_{2}) C. Infrared waves (λ_{3}) D. Microwaves (λ_{4}) Choose the most appropriate answer from the options given below$ (1) $λ_{4} < λ_{3} < λ_{1} < λ_{2}$ (2) $λ_{2} < λ_{1} < λ_{4} < λ_{3}$ (3) $λ_{1} < λ_{2} < λ_{3} < λ_{4}$ (4) $λ_{4} < λ_{3} < λ_{2} < λ_{1}$ 226. $The energy associated with electric field is (U_{E}) and with magnetic field is (U_{B}) for an electromagnetic wave in free space. Then :$ (1) $U_{E} < U_{B}$ (2) $U_{E} = \frac{U _{B}}{2}$ (3) $U_{E} > U_{B}$ (4) $U_{E} = U_{B}$ 227. $The device used to detect infrared radiations is$ (1) $tachometer$ (2) $bolometer$ (3) $photocell$ (4) $point contact diode$ 228. $The structure of solids is investigated by using$ (1) $cosmic rays$ (2) $X ‐rays$ (3) $γ ‐rays$ (4) $infra‐red radiations$ 229. $If μ_{0} is permeability of free space and ϵ_{0} is permittivity of free space, the speed of light in vacuum is given by$ (1) $\frac{1}{μ _{0} ϵ _{0}}$ (2) $\frac{ϵ _{0}}{μ _{0}}$ (3) $μ_{0} ϵ_{0}$ (4) $\frac{μ _{0}}{ϵ _{0}}$ 230. $Two masses m and \frac{m}{2} are connected at the two ends of a massless rigid rod of length l . The road is suspended by a thin wire of torsional constant k at the centre of mass of the rod-mass system (see figure). Because of torsional constant k, the restoring torque is τ = kθ for angular displacement θ . If the rod is rota ted by θ_{0} and released, the tension in it when it passes through its mean position will be:$ (1) $\frac{3 k θ _{0}^{2}}{l}$ (2) $\frac{2 k θ _{0}^{2}}{l}$ (3) $\frac{k θ _{0}^{2}}{l}$ (4) $\frac{k θ _{0}^{2}}{2 l}$ 231. $An electromagnetic wave is represented by the electric field E = E_{0} n sin [ωt + (6 y - 8 z)] Taking unit vectors in x, y and z directions to be i^, j^, k^, the direction of propagation s is:$ (1) $s = \frac{3 i - 4 j}{5}$ (2) $s = \frac{- 4 k + 3 j}{5}$ (3) $s = (\frac{- 3 j + 4 k}{5})$ (4) $s = \frac{3 j - 3 k}{5}$ 232. $Ozone layer blocks the radiations of wavelength$ (1) $more than 3\times 1 0^{- 7} m$ (2) $equal to 3\times 1 0^{- 7} m$ (3) $less than 3\times 1 0^{- 7} m$ (4) $all of these$ 233. $The process of regaining of information from carrier wave at the receiver is termed as$ (1) $demodulation$ (2) $modulation$ (3) $attenuation$ (4) $amplification$ 234. $The correct order of electromagnetic waves with increasing frequency is$ (1) $Infrared, x -rays, gamma rays$ (2) $Gamma rays, visible light, x -rays$ (3) $Visible light, infrared, ultraviolet$ (4) $Visible light, ultraviolet, infrared$ 235. $The electric field and magnetic field components of an electromagnetic wave going through vacuum is described by E_{x} = e0sin (kz - ω t) B_{y} = B0sin (kz - ω t) Then the correct relation between E_{0} and B0 is given by$ (1) $k E_{0} = ω B_{0}$ (2) $E_{0} B_{0} = ωk$ (3) $ω E_{0} = k B_{0}$ (4) $E_{0} = k B_{0}$ 236. $A plane electromagnetic wave propagates along the + x direction in free space. The components of the electric field, E and magnetic field, B vectors associated with the wave in Cartesian frame are$ (1) $E_{x}, B_{y}$ (2) $E_{y}, B_{z}$ (3) $E_{z}, B_{y}$ (4) $E_{y}, B_{x}$ 237. $A linearly polarized electromagnetic wave in vacuum is E = 3.1 cos [(1.8) z - (5.4 \times 1 0^{6}) t] i^N/C is incident normally on a perfectly reflecting wall at z = a. Choose the correct option$ (1) $The wavelength is 5.4m$ (2) $The frequency of electromagnetic wave is 54 \times 1 0^{4} Hz$ (3) $The transmitted wave will be 3.1 cos [(1.8) z - (5.4 \times 1 0^{6}) t] i^N/C$ (4) $The reflected wave will be 1 cos [(1.8) z - (5.4 \times 1 0^{6}) t] i^N/C$ 238. $Identify the correct statements from the following descriptions of various properties of electromagnetic waves. (A) In a plane electromagnetic wave electric field and magnetic field must be perpendicular to each other and direction of propagation of wave should be along electric field or magnetic field. (B) The energy in electromagnetic wave is divided equally between electric and magnetic fields. (C) Both electric field and magnetic field are parallel to each other and perpendicular to the direction of propagation of wave. (D) The electric field, magnetic field and direction of propagation of wave must be perpendicular to each other. (E) The ratio of amplitude of magnetic field to the amplitude of electric field is equal to speed of light. Choose the most appropriate answer from the options given below:$ (1) $D only$ (2) $B and D only$ (3) $B, C and E only$ (4) $A, B and E only$ 239. $In frequency modulated wave$ (1) $frequency varies with time$ (2) $both frequency and amplitude vary with time$ (3) $amplitude varies with time$ (4) $both frequency and amplitude are constant$ 240. $The intensity of the light from a bulb incident on a surface is 0.22 W / m^{2} . The amplitude of the magnetic field in this light-wave is ______\times 1 0^{- 9} T. (Given : Permittivity of vacuum ϵ_{0} = 8.85 \times 1 0^{- 12} C^{2} N^{- 1} m^{- 2}, speed of light in vacuum c = 3 \times 1 0^{8} m s^{- 1})$