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Physics Choose the most appropriate answer from the given alternatives and write the option code and the corresponding answer.

Electromagnetic Waves · Tamil Nadu Board STD 12 (Tamil - English Medium). 30 questions.

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Choose the most appropriate answer from the given alternatives and write the option code and the corresponding answer.

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30 questions · timed · auto-graded

MCQ 11 Mark
Electromagnetic waves are produced by
  • A
    Atoms and molecules in an electrical discharge
  • B
    Electric device
  • ✓
    Accelerated charges
  • D
    Molecules of hot bodies
Answer
Correct option: C.
Accelerated charges
Accelerated charges
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MCQ 21 Mark
The energy in an electromagnetic wave is
  • A
    Wholly shared only by electric field vector
  • B
    Wholly shared only by magnetic field vector
  • ✓
    Equally divided between the electric and magnetic field
  • D
    Zero
Answer
Correct option: C.
Equally divided between the electric and magnetic field
Equally divided between the electric and magnetic field
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MCQ 31 Mark
In an electromagnetic wave the phase difference between electric field $\vec{E}$ and magnetic field $\vec{B}$ is
  • A
    $\frac{\pi}{4}$
  • B
    $\frac{\pi}{2}$
  • C
    $\pi$
  • ✓
    zero
Answer
Correct option: D.
zero
zero
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MCQ 41 Mark
The frequency of a wave is $6 \times 10^{15} Hz$. The wave is
  • A
    Radio wave
  • B
    Microwave
  • C
    X-ray
  • ✓
    UV rays
Answer
Correct option: D.
UV rays
UV rays
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MCQ 51 Mark
An electromagnetic wave of frequency v = 3.0MHz passes from vacuum into a dielectric medium with permitivity s = 4.0 ε0. Then
  • A
    Wavelength is doubled and frequency becomes half
  • B
    Wavelength is doubled and the frequency remains unchanged.
  • C
    avelength and frequency both remain unchanged
  • ✓
     Wavelength is halved and frequency remains unchanged.
Answer
Correct option: D.
 Wavelength is halved and frequency remains unchanged.
Wavelength is halved and frequency remain unchanged.
Hint:When a wave goes from one medium to another, its frequency remains unchanged.According to equation $C=\frac{1}{\sqrt{\mu \varepsilon}}$, the speed is halved. Therefore, the wavelength is also halved.
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MCQ 61 Mark
Electromagnetic radiation of frequency 1 GHz lies in
  • A
     UV region
  • B
    IR region
  • C
     Visible region
  • ✓
     Microwave region
Answer
Correct option: D.
 Microwave region
 Microwave region
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MCQ 71 Mark
Which of the following has maximum frequency?
  • ✓
    X-rays
  • B
     IR rays
  • C
    UV rays
  • D
    Radio waves
Answer
Correct option: A.
X-rays
X-rays.
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MCQ 81 Mark
Radio waves and visible light in a vacuum have
  • A
    Same wavelength but different velocities
  • ✓
    Same velocity but the different wavelength
  • C
    Different velocities and different wavelengths
  • D
    Same velocity and same wavelength
Answer
Correct option: B.
Same velocity but the different wavelength
Same velocity but different wavelength.
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MCQ 91 Mark
Electromagnetic radiation of frequency $3 \times 10^5 MHz$ lies in the
  • A
     Radio wave region
  • B
    Visible region
  • C
    IR region
  • ✓
    Microwave region
Answer
Correct option: D.
Microwave region
Microwave region
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MCQ 101 Mark
An electromagnetic wave has wavelength 10cm. It is in the
  • A
    Visible region
  • ✓
    Radio region
  • C
     UV region
  • D
    X-ray region
Answer
Correct option: B.
Radio region
Radio region
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MCQ 111 Mark
It is possible to take pictures of those objects which are not fully visible to the eye using camera films sensitive to
  • A
    UV rays
  • ✓
    IR rays
  • C
    Microwaves
  • D
    Radio waves
Answer
Correct option: B.
IR rays
IR rays
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MCQ 121 Mark
The ozone layer absorbs radiation of wavelegnths
  • ✓
    Less than $3 \times 10^{-7} m$
  • B
    More than $3 \times 10^{-7} m$
  • C
    Less than $3 \times 10^{-5} m$
  • D
    More than $3 \times 10^{-5} m$
Answer
Correct option: A.
Less than $3 \times 10^{-7} m$
Less than $3 \times 10^{-7} m$.
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MCQ 131 Mark
Which of the following radiations forms part of the electromagnetic spectrum?
  • A
    alpha rays
  • B
    Beta rays
  • ✓
    Gamma rays
  • D
    Cathode rays
Answer
Correct option: C.
Gamma rays
Gamma rays.
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MCQ 141 Mark
The ratio of the amplitude of magnetic field to the amplitude of electric field for an electromagnetic wave propagating in a vacuum is equal to
  • A
    the speed of light in vacuum
  • ✓
    reciprocal of the speed of light in a vacuum
  • C
    the ratio of magnetic permeability to electric susceptibility in vacuum
  • D
    unity
Answer
Correct option: B.
reciprocal of the speed of light in a vacuum
reciprocal of the speed of light in vacuum.
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MCQ 151 Mark
If $\lambda_{ v }, \lambda_{ x }, \lambda_{ m }$, represent the wavelength of visible light, $X$-rays and microwaves, respectively, then
  • A
    $\lambda_m>\lambda_y>\lambda_x$
  • ✓
    $\lambda_m>\lambda_v>\lambda_x$
  • C
    $\lambda_{ v }>\lambda_{ m }>\lambda_{ x }$
  • D
    $\lambda_v>\lambda_x>\lambda_m$
Answer
Correct option: B.
$\lambda_m>\lambda_v>\lambda_x$
$\lambda_m>\lambda_v>\lambda_x$.
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MCQ 161 Mark
Dimensions of $\frac{1}{\mu_0 \varepsilon_0}$ where symbols have their usual meaning, are
  • A
    $\left[ L ^{-2} T ^2\right]$
  • ✓
    $\left[ L ^2 T ^{-2}\right]$
  • C
    $\left[ LT ^{-1}\right]$
  • D
    $\left[ L ^{-1} T \right]$
Answer
Correct option: B.
$\left[ L ^2 T ^{-2}\right]$
$\left[ L ^2 T ^{-2}\right]$Hint:$C =\frac{1}{\sqrt{\mu_0 \varepsilon_0}} \Rightarrow \frac{1}{\mu_0 \varepsilon_0}= C ^2=\left[ L ^2 T ^{-2}\right]$
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MCQ 171 Mark
If $\varepsilon_0$ and $\mu_0$ are the electric permitivity and permeability of free space, $\varepsilon$ and $\mu$ are the corresponding quantities in a medium, then the index of refraction of the medium is
  • A
    $\sqrt{\frac{\varepsilon_0 \mu}{\varepsilon \mu_0}}$
  • B
    $\sqrt{\frac{\varepsilon}{\varepsilon_0}}$
  • C
    $\sqrt{\frac{\varepsilon_0 \mu_0}{\varepsilon \mu}}$
  • ✓
    $\sqrt{\frac{\varepsilon \mu}{\varepsilon_0 \mu_0}}$
Answer
Correct option: D.
$\sqrt{\frac{\varepsilon \mu}{\varepsilon_0 \mu_0}}$
$\sqrt{\frac{\varepsilon \mu}{\varepsilon_0 \mu_0}}$Hint:Index of refraction$\frac{ C }{ C _m}=\frac{1}{\sqrt{\mu_0 \varepsilon_0}} \times \frac{\sqrt{\mu \varepsilon}}{1}=\sqrt{\frac{\mu \varepsilon}{\mu_0 \varepsilon_0}}$
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MCQ 181 Mark
If a capacitance C is connected across an inductance L, then the angular frequency is
  • A
    $\sqrt{L C}$
  • B
    LC
  • C
    $\sqrt{\frac{L}{C}}$
  • ✓
    $\sqrt{\frac{1}{L C}}$
Answer
Correct option: D.
$\sqrt{\frac{1}{L C}}$
$\sqrt{\frac{1}{L C}}$
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MCQ 191 Mark
The greenhouse effect is caused by
  • A
    UV rays
  • B
     X-rays
  • C
    Gamma rays
  • ✓
    IR rays
Answer
Correct option: D.
IR rays
IR rays
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MCQ 201 Mark
The frequencies of X-rays, v-rays and UV rays are respectively a, b and c. Then
  • A
    a < b, b < c
  • ✓
    a < b, b > c
  • C
    a > b, b > c
  • D
    a > b, b < c
Answer
Correct option: B.
a < b, b > c
a < b, b > c
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MCQ 211 Mark
Consider an electric charge oscillating with frequency of 10MHz. The radiation emitted will have a wavelength eqal to
  • A
    20m
  • ✓
    30m
  • C
    40m
  • D
    10m
Answer
Correct option: B.
30m
30
Hint:
Wave length, $\lambda=\frac{C}{v}=\frac{3 \times 10^8}{10 \times 10^6}$ $=0.3 \times 10^2=30 m$.
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MCQ 221 Mark
The electromagnetic radiation most prevalent in the atmosphere is
  • A
    Visible light
  • ✓
    Infrared
  • C
    UV
  • D
    Radio waves
Answer
Correct option: B.
Infrared
Infrared.
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MCQ 231 Mark
TV waves have a wavelength range of 1 – 10 metre. Their frequency range in MHz is
  • A
    300 – 3000
  • B
    3 – 3000
  • ✓
    30 – 300
  • D
     3 – 30
Answer
Correct option: C.
30 – 300
30 – 300.
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MCQ 241 Mark
Which of the following radiations has the longest wavelength?
  • ✓
    Radio waves
  • B
     IR radiation
  • C
     X-ray
  • D
    Visible light
Answer
Correct option: A.
Radio waves
 Radio waves.
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MCQ 251 Mark
A RADAR beam consists of
  • A
    X-rays
  • B
    IR rays
  • C
     UV rays
  • ✓
     Microwaves
Answer
Correct option: D.
 Microwaves
 Microwaves
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MCQ 261 Mark
Ozone layer absorbs
  • A
     Infrared radiation
  • B
    Microwaves
  • C
    Radio waves
  • ✓
    UV radiation
Answer
Correct option: D.
UV radiation
UV radiation
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MCQ 271 Mark
In which of the following sequences are the electro magnetic radiations in decreasing order of wavelength
  • A
    Infrared, radio, X-rays, visible
  • ✓
    Radio, infrared, visible, X-rays
  • C
     Radio, visible, infrared, X-rays
  • D
     X-rays, visible, infrared, radio
Answer
Correct option: B.
Radio, infrared, visible, X-rays
Radio, infrared, visible, X-rays
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MCQ 281 Mark
If E and B be the electric and magnetic field vectors of an electromagnetic wave, then the propagation of the wave is along the direction of
  • A
    E
  • B
    B
  • ✓
    E x B
  • D
    Bx E
Answer
Correct option: C.
E x B
E x B.
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MCQ 291 Mark
In an electromagnetic wave, the electric field vector $E$ and magnetic field vector $B$ are
  • ✓
    Perpendicular to each other
  • B
    Parallel to each other
  • C
    at $45^{\circ}$ to each other
  • D
    can have any angle between them
Answer
Correct option: A.
Perpendicular to each other
Perpendicular to each other.
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MCQ 301 Mark
The speed of electromagnetic waves in vacuum is given by
  • A
    $\mu_0 \varepsilon_0$
  • B
    $\sqrt{\mu_0 \varepsilon_0}$
  • C
    $\frac{1}{\mu_0 \varepsilon_0}$
  • ✓
    $\frac{1}{\sqrt{\mu_0 \varepsilon_0}}$
Answer
Correct option: D.
$\frac{1}{\sqrt{\mu_0 \varepsilon_0}}$
$\frac{1}{\sqrt{\mu_0 \varepsilon_0}}$
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Choose the most appropriate answer from the given alternativ - Physics STD 12 Questions - Vidyadip