Electromagnetic Waves PYQs Set 6 (PDF)

Set 6 of 9 · Questions 151-180 of 253

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Mere Teacher · Previous Year Questions JEE Main Physics · Electromagnetic Waves · Set 6 (Q151-180)
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151. $In a Young's double slit experiment, a student observes 8 fringes in a certain segment of screen when a monochromatic light of 600 nm wavelength is used. If the wavelength of light is changed to 400 nm, then the number of fringes he would observe in the same region of the screen is [NEET 2022]$ (1) $8$ (2) $9$ (3) $12$ (4) $6$ 152. $The unit of \frac{2 I}{ϵ _{0} c} is: (I = intensity of an electromagnetic wave, c = speed of light)$ (1) $Vm$ (2) $NC^{- 1}$ (3) $NC$ (4) $Nm$ 153. $In a plane electromagnetic wave, the maximum value of the electric field component is 4.4 Vm^{- 1} . The intensity of the wave is nearly$ (1) $22.4 mW m^{- 2}$ (2) $25.7 mW m^{- 2}$ (3) $65.5 mW m^{- 2}$ (4) $45.6 mW m^{- 2}$ 154. $The speed of electromagnetic waves in a medium is 1.5 \times 10^{8} ms^{- 1} . If relative permittivity of that medium is 2 , then its magnetic susceptibility is (speed of light in vacuum is 3 \times 10^{8} ms^{- 1}).$ (1) $2$ (2) $3$ (3) $1$ (4) $-1.5$ 155. $In a diffraction pattern due to a single slit of width , the first minimum is observed at an angle when light of wavelength is incident on the slit. The first secondary maximum is observed at an angle of [NEET 2016]$ (1) $sin^{- 1} (\frac{2}{3})$ (2) $sin^{- 1} (\frac{1}{2})$ (3) $sin^{- 1} (\frac{3}{4})$ (4) $sin^{- 1} (\frac{1}{4})$ 156. $If E and K represent electric field and propagation vectors of the EM waves in vacuum, then magnetic field vector is given by: (ω -angular frequency):$ (1) $\frac{1}{ω} (K \times E)$ (2) $ω (E \times K)$ (3) $ω K \times E$ (4) $K \times E$ 157. $Practically ozone layer absorbs radiations of wavelength$ (1) $less than 3\times 1 0^{- 7} m$ (2) $greater than 3\times 1 0^{- 7} m$ (3) $equal to 3\times 1 0^{- 7} m$ (4) $All of the above$ 158. $The electric field of an electromagnetic wave in free space is E = 57 cos (7.5 \times 10^{6} t - 5 \times 10^{- 3} (3 x + 4 y)) (4 i - 3 j) N / C . The associated magnetic field in Tesla is$ (1) $B = \frac{57}{3} \times 1 0^{- 8} cos (7.5 \times 1 0^{6} t - 5 \times 1 0^{- 3} (3 x + 4 y)) (k^)$ (2) $B = - \frac{57}{3} \times 1 0^{- 8} cos (7.5 \times 1 0^{6} t - 5 \times 1 0^{- 3} (3 x + 4 y)) (k^)$ (3) $B = - \frac{57}{3} \times 1 0^{- 8} cos (7.5 \times 1 0^{6} t - 5 \times 1 0^{- 3} (3 x + 4 y)) (5 k^)$ (4) $B = \frac{57}{3} \times 1 0^{- 8} cos (7.5 \times 1 0^{6} t - 5 \times 1 0^{- 3} (3 x + 4 y)) (5 k^)$ 159. $The Brewster's angle I_{B} for an interface should be [NEET 2020]$ (1) $30^{\circ} < I_{B} < 45^{\circ}$ (2) $45^{\circ} < I_{B} < 90^{\circ}$ (3) $I_{B} = 90^{\circ}$ (4) $0^{\circ} < I_{B} < 30^{\circ}$ 160. $A 27 mW laser beam has a cross-sectional area of 10 mm^{2} . The magnitude of the maximum electric field in this electromagnetic wave is given by: [Given permittivity of space ϵ_{0} = 9 \times 10^{- 12} SI units, Speed of light c = 3 \times 10^{8} m / s]$ (1) $2 kV / m$ (2) $0.7 kV / m$ (3) $1 kV / m$ (4) $1.4 kV / m$ 161. $Electromagnetic waves travel in a medium with speed of 1.5 \times 10^{8} m s^{- 1} . The relative permeability of the medium is 2.0 . The relative permittivity will be:$ (1) $2$ (2) $4$ (3) $5$ (4) $1$ 162. $If the magnetic field of a plane electromagnetic wave is given by (The speed of light (= 3 \times 10^{8} m / s) B = 100 \times 10^{- 6} sin (2 π \times 2 \times 10^{15} (t - \frac{x}{c})) then the maximum electric field associated with it is:$ (1) $6 \times 10^{4} N / C$ (2) $3 \times 10^{4} N / C$ (3) $4 \times 10^{4} N / C$ (4) $4.5 \times 10^{4} N / C$ 163. $A plane electromagnetic wave is moving in free space with velocity c = 3 \times 10^{8} m / s and its electric field is given as E = 54 sin (kz - ωt) j V / m, where j is the unit vector along y -axis. The magnetic field vector B of the wave is:$ (1) $+ 1.8 \times 10^{- 7} sin (kz - ωt) i T$ (2) $1.4 \times 10^{- 7} sin (kz - ωt) k T$ (3) $- 1.8 \times 10^{- 7} sin (kz - ωt) i T$ (4) $1.4 \times 10^{- 7} sin (kz - ωt) i T$ 164. $The amplitude of magnetic field in an electromagnetic wave propagating along y-axis is 6.0 x 1 0^{- 7} T. The maximum value of electric field in the electromagnetic wave is$ (1) $2 x 1 0^{15} V m^{- 1}$ (2) $180 V m^{- 1}$ (3) $6.0 x 1 0^{- 7} V m^{- 1}$ (4) $5 x 1 0^{14} V m^{- 1}$ 165. $A parallel plate capacitor is charged by connecting it to a battery through a resistor. If I is the current in the circuit, then in the gap between the plates [NEET 2024]$ (1) $There is no current$ (2) $Displacement current of magnitude equal to I flows in the same direction as I$ (3) $Displacement current of magnitude equal to I flows in a direction opposite to that of I$ (4) $Displacement current of magnitude greater than I flows but can be in any direction$ 166. $If the average power per unit area delivered by an electromagnetic wave is 9240 Wm^{- 2}, then the amplitude of the oscillating magnetic field in EM wave is$ (1) $4.4 μ T$ (2) $6.6 μ T$ (3) $8.8 μ T$ (4) $10.2 μ T$ 167. $The interference pattern is obtained with two coherent light sources of intensity ratio n . In the interference pattern, the ratio \frac{I _{max} - I _{min}}{I _{max} + I _{min}} will be [NEET 2016]$ (1) $\frac{n}{n + 1}$ (2) $\frac{2 n}{n + 1}$ (3) $\frac{n}{( n + 1 ) ^{2}}$ (4) $\frac{2 n}{( n + 1 ) ^{2}}$ 168. $The magnetic field of a plane electromagnetic wave is given by B = 2 \times 1 0^{- 8} sin (0.5 \times 1 0^{3} x + 1.5 \times 1 0^{11} t) j T The amplitude of the electric field would be$ (1) $6 V m^{- 1} along x-axis$ (2) $3 V m^{- 1} along z-axis$ (3) $6 V m^{- l} along z-axis$ (4) $2 x 1 0^{- 8} V m^{- 1} along z-axis$ 169. $If frequency of electromagnetic wave is 60 MHz and it travels in air along z direction then the corresponding electric and magnetic field vectors will be mutually perpendicular to each other and the wavelength of the wave (in m) is:$ (1) $2.5$ (2) $10$ (3) $5$ (4) $2$ 170. $Match List -1 with List - II List I (A) UV rays (B) X-rays (C) Microwave (D) Infrared wave List II (I) Diagnostic tool in medicine (II) Water purification (III) Communication, Radar (IV) Improving visibility in foggy days Choose the correct answer from the options given below:$ (1) $(A)-(III), (B)-(II), (C)-(I), (D)-(IV)$ (2) $(A)-(II), (B)-(I), (C)-(III), (D)-(IV)$ (3) $(A)-(II), (B)-(IV), (C)-(III), (D)-(I)$ (4) $(A)-(III), (B)-(I), (C)-(II), (D)-(IV)$ 171. $A plane electromagnetic wave travels in free space along z -axis. At a particular point in space, the electric field along x -axis is 8.7 Vm^{- 1} . The magnetic field along y -axis is$ (1) $2.9 \times 10^{- 8} T$ (2) $3 \times 10^{- 6} T$ (3) $8.7 \times 10^{- 6} T$ (4) $3 \times 10^{- 5} T$ 172. $To heat the food containing water, the frequency of the microwaves used in microwave oven is$ (1) $independent of the resonant frequency of water molecules.$ (2) $equal to the resonant frequency of water molecules.$ (3) $100 times the resonant frequency of water molecules.$ (4) $\frac{1}{100} times the resonant frequency of water molecules.$ 173. $In a Young's double slit experiment, if there is no initial phase difference between the light from the two slits, a point on the screen corresponding to the fifth minimum has path difference is [NEET 2019]$ (1) $5 \frac{λ}{2}$ (2) $10 \frac{λ}{2}$ (3) $9 \frac{λ}{2}$ (4) $11 \frac{λ}{2}$ 174. $Match the electromagnetic radiations given in List -1 with their uses given in List - II. List - I (A) X-rays (B) UV-rays (C) Radio waves (D) IR - rays List - II (P) Remote switches (Q) Finger prints in forensic Labs (R) Crystal structure Study (S) TV communication system.$ (1) $A \to Q, B \to R, C \to P, D \to S$ (2) $A \to R, B \to Q, C \to S, D \to P$ (3) $A \to R, B \to S, C \to Q, D \to P$ (4) $A \to S, B \to R, C \to Q, D \to P$ 175. $In which of the following, emission of electrons does not take place$ (1) $thermionic emission$ (2) $X ‐rays emission$ (3) $photoelectric emission$ (4) $secondary emission$ 176. $Which of the following electromagnetic radiations have the smaller wavelength?$ (1) $X ‐rays$ (2) $γ ‐rays$ (3) $UV waves$ (4) $microwaves.$ 177. $A linear aperture whose width is 0.02 cm is placed immediately in front of a lens of focal length 60 cm. The aperture is illuminated normally by a parallel beam of wavelength . The distance of the first dark band of the diffraction pattern from the center of the screen is [NEET 2016]$ (1) $0.10 cm$ (2) $0.25 cm$ (3) $0.20 cm$ (4) $0.15 cm$ 178. $Which of the following electromagnetic radiations have the longest wavelength?$ (1) $X ‐rays$ (2) $Y ‐rays$ (3) $Microwaves$ (4) $Radiowaves$ 179. $The decreasing order of wavelength of infrared, microwave, ultraviolet and gamma rays is$ (1) $microwave, infrared, ultraviolet, gamma rays$ (2) $gamma rays, ultraviolet, infrared, microwaves$ (3) $microwaves, gamma rays, infrared, ultraviolet$ (4) $infrared, microwave, ultraviolet, gamma rays$ 180. $A radiation is emitted by 1000 W bulb and it generates an electric field and magnetic field at P_{t} placed at a distance of 2m. The efficiency of the bulb is 1.25%. The value of peak electric field at P is x \times 10^{- 1} V / m . Value of x is ____. (Rounded-off to the nearest integer) [Take ϵ_{0} = 8.85 \times 10^{- 12} C^{2} N^{- 1} m^{- 2}, c = 3 \times 10^{8} m s^{- 1}]$