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#1 Class 12 Physics Electromagnetic Waves 2022 Mcq 1M CBSE
Match the following EM waves with their applications: Microwaves — P. Treatment of cancer Infrared — Q. Aircraft navigation (radar) UV rays — R. Remote controls Gamma rays — S. Water purification The correct match is
A. 1-P, 2-R, 3-S, 4-Q
B. 1-S, 2-P, 3-Q, 4-R
C. 1-Q, 2-R, 3-S, 4-P
D. 1-S, 2-R, 3-P, 4-Q
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#2 Class 12 Physics Electromagnetic Waves 2021 Mcq 1M CBSE
Which of the following statements is true for radio waves and gamma rays?
A. The energy of gamma rays is lesser than that of radio waves
B. The frequency of radio waves is higher than that of gamma rays
C. Radio waves and gamma rays have the same energy
D. The energy of radio waves is lesser than that of gamma rays
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#3 Class 12 Physics Electromagnetic Waves 2022 Long 1M CBSE
Assertion: Microwaves are better carriers of signals than optical waves. Reason: Microwaves move faster than optical waves.
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#4 Class 12 Physics Electromagnetic Waves 2020 Short 2M CBSE
An electromagnetic wave passing through vacuum is described by $E = E_0\sin(kx - \omega t)$ and $B = B_0\sin(kx - \omega t)$. Write the relations between $E_0$, $B_0$, $k$, $\omega$ and $c$.
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#5 Class 12 Physics Electromagnetic Waves 2019 Mcq 1M CBSE
Which of the following electromagnetic waves has the minimum frequency?
A. radio waves
B. ultrasonic waves
C. audible waves
D. microwaves
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#6 Class 12 Physics Electromagnetic Waves 2021 Mcq 1M CBSE
An electromagnetic wave of frequency 3 MHz passes from vacuum into a medium with dielectric constant $k = 4$. Then
A. both wavelength and frequency remain unchanged
B. wavelength is doubled and frequency becomes half
C. wavelength is halved and frequency remains unchanged
D. wavelength is doubled and frequency remains unchanged
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#7 Class 12 Physics Electromagnetic Waves 2020 Mcq 1M CBSE
Which radiation in sunlight causes the heating effect?
A. ultraviolet
B. infrared
C. visible light
D. all of these
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#8 Class 12 Physics Electromagnetic Waves 2019 Mcq 1M CBSE
Which of the following is/are NOT electromagnetic waves?
A. $\beta$-rays
B. X-rays
C. cosmic rays
D. both (a) and (b)
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#9 Class 12 Physics Electromagnetic Waves 2018 Mcq 1M CBSE
The waves which CANNOT travel in vacuum are
A. X-rays
B. radio waves
C. infrasonic waves
D. ultraviolet waves
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#10 Class 12 Physics Electromagnetic Waves 2020 Mcq 1M CBSE
According to Maxwell's displacement current law, a changing electric field is the source of
A. an emf
B. magnetic field
C. pressure gradient
D. all of these
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#11 Class 12 Physics Electromagnetic Waves 2019 Mcq 1M CBSE
The displacement current exists in a region where the electric field
A. increases with time
B. decreases with time
C. attains a constant value
D. both (a) and (b)
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#12 Class 12 Physics Electromagnetic Waves 2012 Mcq 1M CBSE
The idea of displacement current was introduced by
A. Hertz
B. Ampere
C. Maxwell
D. Faraday
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#13 Class 12 Physics Electromagnetic Waves 2020 Mcq 1M CBSE
The unit of the ratio of magnetic field $B$ to electric field $E$ ($B/E$) is
A. m s$^{-1}$
B. s m$^{-1}$
C. m s
D. s$^{-2}$
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#14 Class 12 Physics Electromagnetic Waves 2021 Short 1M CBSE
What is the phase difference between the electric field $\vec{E}$ and magnetic field $\vec{B}$ in an electromagnetic wave propagating in vacuum?
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#15 Class 12 Physics Electromagnetic Waves 2020 Mcq 1M CBSE
If $\vec{E}$ and $\vec{B}$ represent electric and magnetic field vectors of an electromagnetic wave, the direction of propagation of the wave is along
A. $\vec{E}$
B. $\vec{B}$
C. $\vec{B} \times \vec{E}$
D. $\vec{E} \times \vec{B}$
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#16 Class 12 Physics Electromagnetic Waves 2019 Mcq 1M CBSE
The electromagnetic waves used to purify water are
A. Infrared rays
B. Ultraviolet rays
C. X-rays
D. Gamma rays
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#17 Class 12 Physics Alternating Current 2023 Short 3M CBSE
A transformer having efficiency of 90% is working on 200 V and 3 kW power supply. If the current in the secondary coil is 6 A, find: (a) the voltage across the secondary coil, (b) the current in the primary coil.
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#18 Class 12 Physics Alternating Current 2021 Short 2M CBSE
A transformer is used to light a 100 W, 110 V lamp from 220 V mains. If the primary current is 0.5 A, find the efficiency of the transformer.
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#19 Class 12 Physics Alternating Current 2022 Short 3M CBSE
A 220 V input is supplied to a transformer. The output circuit draws a current of 2.0 A at 440 V. If the efficiency of the transformer is 80%, find the current drawn by the primary windings.
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#20 Class 12 Physics Alternating Current 2020 Short 2M CBSE
The primary winding of a transformer has 500 turns and the secondary has 5000 turns. The primary is connected to AC supply of 20 V, 50 Hz. What will be the output of the secondary?
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