Electromagnetic Waves PYQs Set 1 (PDF)

Set 1 of 9 · Questions 1-30 of 253

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Mere Teacher · Previous Year Questions JEE Main Physics · Electromagnetic Waves · Set 1 (Q1-30)
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1. $Two coherent sources of light interfere and produce fringe pattern on a screen. For central maximum, the phase difference between the two waves will be [NEET 2020]$ (1) $zero$ (2) $π$ (3) $3 π /2$ (4) $π /2$ 2. $The ratio of average electric energy density and total average energy density of electromagnetic wave is:$ (1) $2$ (2) $1$ (3) $3$ (4) $\frac{1}{2}$ 3. $The oscillating magnetic field in a plane electromagnetic wave is given by B_{y} = 5 \times 1 0^{- 6} sin 1000 π (5 x - 4 \times 1 0^{8} t) T . The amplitude of electric field will be:$ (1) $15 x 1 0^{2} V m^{- 1}$ (2) $5 x 1 0^{- 6} V m^{- 1}$ (3) $16 x 1 0^{12} V m^{- 1}$ (4) $4 x 1 0^{2} V m^{- 1}$ 4. $The ratio of contributions made by the electric field and magnetic field components, to the intensity of an electromagnetic wave is (where, c = speed of electromagnetic waves) [NEET 2020]$ (1) $1 : 1$ (2) $1 : c$ (3) $1 : c^{2}$ (4) $c : 1$ 5. $In an electromagnetic wave in free space the root mean square value of the electric field is E_{rms} = 6 Vm^{- 1} . The peak value of the magnetic field is [NEET 2017]$ (1) $2.83 \times 10^{- 8} T$ (2) $0.70 \times 10^{- 8} T$ (3) $4.23 \times 10^{- 8} T$ (4) $1.41 \times 10^{- 8} T$ 6. $Two slits in Young's experiment have widths in the ratio 1 : 25 . The ratio of intensity at the maxima and minima in the interference pattern \frac{I _{max}}{I _{min}} is$ (1) $\frac{9}{4}$ (2) $\frac{121}{49}$ (3) $\frac{49}{121}$ (4) $\frac{4}{9}$ 7. $A plane electromagnetic wave propagating in x -direction is described by E_{y} = (200 Vm^{- 1}) sin (1.5 \times 10^{7} t - 0.05 x); The intensity of the wave is : (Use ϵ_{0} = 8.85 \times 10^{- 12} C^{2} N^{- 1} m^{- 2})$ (1) $35.4 Wm^{- 2}$ (2) $53.1 Wm^{- 2}$ (3) $26.6 Wm^{- 2}$ (4) $106.2 Wm^{- 2}$ 8. $The electric and magnetic field of an electromagnetic wave are$ (1) $in opposite phase and perpendicular to each other$ (2) $in opposite phase and parallel to each other$ (3) $in phase and perpendicular to each other$ (4) $in phase and parallel to each other.$ 9. $Angular width of the central maxima in the Fraunhofer diffraction for is . When the same slit is illuminated by another monochromatic light, the angular width decreases by . The wavelength of this light is [NEET 2019]$ (1) $1800Å$ (2) $4200Å$ (3) $6000Å$ (4) $420Å$ 10. $A layer of atmosphere that reflects medium frequency radio waves which is ineffective during night is$ (1) $F layer$ (2) $Stratosphere$ (3) $E layer$ (4) $Thermosphere$ 11. $Light wave traveling in air along x-direction is given by E_{y} = 540 sin π \times 1 0^{4} (x - ct) V m^{- 1} . Then, the peak value of magnetic field of wave will be (Given c = 3 x 108 m s^{- 1})$ (1) $18 x 1 0^{- 7} T$ (2) $54 x 1 0^{- 7} T$ (3) $54 x 1 0^{- 8} T$ (4) $18 x 1 0^{- 8} T$ 12. $The electric field part of an electromagnetic wave in a medium is represented by E_{x} = 0; E_{y} = 2.5 \frac{N}{C} cos [(2 π \times 1 0^{6} \frac{rad}{m}) t - (π \times 1 0^{- 2} \frac{rad}{s}) x]; E_{z} = 0 . The wave is$ (1) $moving along x direction with frequency 1 0^{6} Hz and wavelength 100 m.$ (2) $moving along x direction with frequency 1 0^{6} Hz and wavelength 200m.$ (3) $moving along - x direction with frequency 1 0^{6} Hz and wavelength 200m.$ (4) $moving along y direction with frequency 2 π \times 1 0^{6} Hz and wavelength 200 m.$ 13. $The electric and the magnetic field, associated with an e . m . wave, propagating along the + z ‐axis, can be represented by$ (1) $(E = E_{0} i, B = B_{0} j)$ (2) $(E = E_{0} k, B = B_{0} i)$ (3) $(E = E_{0} j, B = B_{0} i)$ (4) $(E = E_{0} j, B = B_{0} k)$ 14. $A plane electromagnetic wave is propagating along the direction \frac{i ^ + j ^}{2}, with its polarization along the direction k^. The correct from of the magnetic field of the wave would be (here B_{0} is an appropriate constant) :$ (1) $B_{0} \frac{i ^ + j ^}{2} cos (ω t - k \frac{i ^ + j ^}{2})$ (2) $B_{0} \frac{i ^ - j ^}{2} cos (ω t + k \frac{i ^ + j ^}{2})$ (3) $B_{0} \frac{i ^ - j ^}{2} cos (ω t - k \frac{i ^ + j ^}{2})$ (4) $B_{0} k^cos (ω t - k \frac{i ^ + j ^}{2})$ 15. $In Young’s double slit experiment, the slits are 2 mm apart and are illuminated by photons of two wavelength λ_{1} = 12000 Å and λ_{2} = 10000 Å. At what minimum distance from the common central bright fringe on the screen 2 m from the slit will a bright fringe from one interference pattern coincide with a bright fringe from the other?$ (1) $6 mm$ (2) $4 mm$ (3) $3 mm$ (4) $8 mm$ 16. $The magnetic field of an E.M. wave is given by B = (\frac{3}{2} i + \frac{1}{2} j) 30 sin (ω (t - \frac{z}{c})) (S.I. Units). The corresponding electric field in S.I. units is :$ (1) $E = (\frac{1}{2} i - \frac{3}{2} j) 30 c sin (ω (t - \frac{z}{c}))$ (2) $E = (\frac{3}{4} i + \frac{1}{4} j) 30 c cos (ω (t - \frac{z}{c}))$ (3) $E = (\frac{1}{2} i + \frac{3}{2} j) 30 c sin (ω (t + \frac{z}{c}))$ (4) $E = (\frac{3}{2} i - \frac{1}{2} j) 30 c sin (ω (t + \frac{z}{c}))$ 17. $The source of electromagnetic wave can be a charge$ (1) $moving with a constant velocity$ (2) $moving in a circular orbit$ (3) $at rest$ (4) $moving parallel to the magnetic field.$ 18. $The ratio of speeds of electromagnetic waves in vacuum and a medium, having dielectric constant k = 3 and permeability of μ = 2 μ_{0}, is (μ_{0} = permeability of vacuum)$ (1) $36 : 1$ (2) $3 : 2$ (3) $6 : 1$ (4) $6 : 1$ 19. $An electromagnetic wave of intensity enters in a medium of refractive index ' without any loss. The ratio of the magnitudes of electric fields, and the ratio of the magnitudes of magnetic fields of the wave before and after entering into the medium are respectively, given by:$ (1) $(\frac{1}{n}, \frac{1}{n})$ (2) $(n, n)$ (3) $(n, \frac{1}{n})$ (4) $(\frac{1}{n}, n)$ 20. $A 2 mW laser operates at a wavelength of 500 nm . The number of photons that will be emitted per second is: [Given Planck's constant h = 6.6 \times 10^{- 34} Js speed of light (c = 3.0 \times 10^{8} m / s)$ (1) $5 \times 10^{15}$ (2) $1.5 \times 10^{16}$ (3) $2 \times 10^{16}$ (4) $1 \times 10^{16}$ 21. $The velocity of electromagnetic radiation in a medium of permittivity ϵ_{0} and permeability μ_{0} is given by$ (1) $\frac{1}{μ _{0} ϵ _{0}}$ (2) $\frac{μ _{0}}{ϵ _{0}}$ (3) $\frac{ϵ _{0}}{μ _{0}}$ (4) $μ_{0} ϵ_{0}$ 22. $A plane electromagnetic wave travels in a medium of relative permeability 1.61 and relative permittivity 6.44. If magnitude of magnetic intensity is 4.5 x 10-2 A m^{- 1} at a point, what will be the approximate magnitude of electric field intensity at that point? (Given: permeability of free space μ_{0} = 4 π \times 1 0^{- 7} N A^{- 2}, speed of light in vacuum c = 3 x 108 m s^{- 1})$ (1) $16.96 V m^{- 1}$ (2) $2.25 x 1 0^{- 2} V m^{- 1}$ (3) $8.48 V m^{- 1}$ (4) $6.75 x 1 0^{6} V m^{- 1}$ 23. $The electric and the magnetic fields associated with an electromagnetic wave propagating along the z -axis, can be represented by$ (1) $(E = E_{0} i, B = B_{0} j)$ (2) $(E = E_{0} k, B = B_{0} i)$ (3) $(E = E_{0} j, B = B_{0} i)$ (4) $(E = E_{0} j, B = B_{0} k)$ 24. $A plane electromagnetic wave of frequency 35 MHz travels in free space along the X-direction. At a particular point (in space and time) E = 9.6 j V / m . The value of magnetic field at this point is :$ (1) $3.2 \times 10^{- 8} kT$ (2) $3.2 \times 10^{- 8} i T$ (3) $9.6 j T$ (4) $9.6 \times 10^{- 8} k T$ 25. $In communication system, the process of superimposing a low frequency signal on a high frequency wave is known as$ (1) $Repeater$ (2) $Attenuation$ (3) $Modulation$ (4) $Demodulation$ 26. $Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R Assertion A : EM waves used for optical communication have longer wavelengths than that of microwave, employed in Radar technology. Reason R : Infrared EM waves are more energetic than microwaves, (used in Radar) In the light of given statements, choose the correct answer from the options given below.$ (1) $Both A and R are true but R is NOT the correct explanation of A$ (2) $A is false but R is true$ (3) $A is true but R is false$ (4) $Both A and R are true and R is the correct explanation of A$ 27. $If and are the electric permittivity and magnetic permeability in a free space, and are the corresponding quantities in medium, the index of refraction of the medium is$ (1) $\frac{ϵ _{0} μ _{0}}{ϵ μ}$ (2) $\frac{ϵ μ}{ϵ _{0} μ _{0}}$ (3) $\frac{ϵ _{0} μ}{ϵ μ _{0}}$ (4) $\frac{ϵ}{ϵ _{0}}$ 28. $The electric field associated with an em wave in vacuum is given by (E = i 40 cos (kz - 6 \times 1 0^{8} t)) where E, z and t are in volt/m, meter and seconds respectively. The value of wave vector k is$ (1) $2 m^{- 1}$ (2) $0.5 m^{- 1}$ (3) $6 m^{- 1}$ (4) $3 m^{- 1}$ 29. $Light with an energy flux of 9 Wcm^{- 2} falls on a nonreflecting surface at normal incidence. If the surface has an area of 20 cm^{2} . The total momentum delivered for complete absorption in one hour is$ (1) $2.16 \times 10^{- 4} kgms^{- 1}$ (2) $1.16 \times 10^{- 3} kgms^{- 1}$ (3) $2.16 \times 10^{- 3} kgms^{- 1}$ (4) $3.16 \times 10^{- 4} kgms^{- 1}$ 30. $Match List-I with List-II : List-I EM-Wave (A) Infra-red (B) Ultraviolet (C) X-rays S (D) Gamma rays List-II Wavelength Range (I) < 10^{- 3} nm (II) 400 nm to 1 nm (III) 1 mm to 700 nm (IV) 1 nm to 10^{- 3} nm$ (1) $(A)-(III), (B)-(II), (C)-(IV), (D)-(I)$ (2) $(A)-(II), (B)-(I), (C)-(IV), (D)-(III)$ (3) $(A)-(IV), (B)-(III), (C)-(II), (D)-(I)$ (4) $(A)-(I), (B)-(III), (C)-(II), (D)-(IV)$