MCQ Questions for Class 12 Medical Physics Electromagnetic Waves Quiz 1

Some radio waves of frequency of about

$1.5\times 10^9$ Hz was received by a radio-telescope from distance star. If the speed of the waves is

$3\times 10^5$ km/s, then the wave-length of the wave will be?

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$0.1$ m
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$0.6$ m
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$0.2$ m
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$0.46$ m

The energy of photon of electromagnetic radiation of wavelength

$=2000\mathring{A}$ is?

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$1.76\times 10^{-18}$ J
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$0.99\times 10^{-18}$ J
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$0.54\times 10^{-18}$ J
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$0.63\times 10^{-18}$ J

A radio wave of intensity l is reflected by a surface. The intensity (I), if pressure exerted on the surface is

$2\times 10^{-8}N/m^2$ , will be?

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$3 N/m^2$
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$4 N/m^2$
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$6 N/m^2$
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$7 N/m^2$

A TV tower has a height of

$100$ m. The area covered by the TV broadcast, if radius of the earth is

$6400$ km, will be?

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$380\times 10^7m^2$
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$402\times 10^7m^2$
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$595\times 10^7m^2$
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$440\times 10^7m^2$

The current option, if speed of gamma rays, X-rays and microwaves are

$v_g, v_x$ and

$v_m$ respectively will be?

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$v_g > v_x > v_m$
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$v_g < v_x < v_m$
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$v_g > v_x < v_m$
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$v_g = v_x = v_m$

Arrange the following electromagnetic radiations per quantum in the order of increasing energy:
A: Blue light
B: Yellow light
C: X-ray
D: Radiowave

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D,B,A,C
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A,B,D,C
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C,A,B,D
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B,A,D,C

What is the displacement current between the square plate of side 1 cm of a capacitor, if electric field between the, plates is changing at the rate of 3 x

$10^6 V_m^{-1}S^{-1}$ ?

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2.7 x $10^{-9}$ A
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3.2 x $10^{-9}$ A
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4.2 x $10^{-9}$ A
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4.0 x $10^{-9}$ A

Choose the correct equation of maxwell ampere circuital law:

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$\oint \overline { B } \cdot \overline { d l } = \mu _ { 0 } \varepsilon _ { 0 } \frac { d \phi _ { E } } { d t }$
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$\oint \overline { B } \cdot \overline { d l } = \mu _ { 9 } + \varepsilon _ { 0 } \frac { d \phi _ { E } } { d t }$
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$\oint \vec { B } \cdot \overline { d l } = \mu _ { 0 } \left( i _ { c } + \varepsilon _ { 0 } \frac { d \phi _ { E } } { d t } \right)$
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$\oint \overline { B } \cdot \overline { d l } = \mu _ { 0 } i _ { C } + \varepsilon _ { 0 } \frac { d \phi _ { \varepsilon } } { d t }$

Which of the following sources of light is different from others

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Sunlight
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White light
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Light from a bulb
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Sodium light

Which wavelength of sun is used finally as electric energy?

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Radio waves
0%
Infrared waves
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Visible light
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Micro waves

Magnetic field in a plane electromagnetic wave is given by

$\overrightarrow{B} = B_0 sin (kx + \omega t) \hat{j} T$
Expression for corresponding electric field will be :
Where c is speed of light.

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$\overrightarrow {E} = B_0 c\sin (kx + \omega t) \hat{k} V/m$
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$\overrightarrow{E} = \dfrac{B_0}{c} \sin (kx + \omega t) \hat{k} V/m$
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$\overrightarrow {E} = - B_0 c \sin (kx + \omega t) \hat{k} V/m$
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$\overrightarrow{E} = B_0 c \sin (kx - \omega t) \hat{k} V/m$

Explanation

$\dfrac{\overrightarrow{E}}{\overrightarrow{B}}=C$

$\overrightarrow{B} = B_0\sin(kx + \omega t)$

$\overrightarrow {E} = B_0C\sin(kx+\omega t)\hat k$

$V/m$

Match the List -I (Phenomenon associated with electromagnetic radiation) with List - II (Part of electromagnetic spectrum) and select the correct code from the choices given below the

	List - I		List - II
I	Doublet of sodium	A	Visible radiation
II	Wavelength corresponding to temperature associated with the isotropic radiation filling all space	B	Microwave
III	Wavelength emitted by atomic hydrogen in interstellar space	C	Short radiowave
IV	Wavelength of radiation arising from two close energy levels in hydrogen	D	X-rays

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(I)-(A), (II)-(B), (III)-(B), (IV)-(C)
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(I)-(D), (II)-(C), (III)-(A), (IV)-(B)
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(I)-(B), (II)-(A), (III)-(D), (IV)-(A)
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(I)-(A), (II)-(B), (III)-(C), (IV)-(D)

Explanation

$Doublet \ of \ sodium$

$\Rightarrow$

$X-rays$

$Wavelength \ corresponding \ to \ temperature \ associated \ with \ the \ isotropic \ radiation \ filling \ all \ space$

$\Rightarrow$

$Short \ radiowave$

$Wavelength \ emitted \ by \ atomic \ hydrogen \ in \ interstellar \ space$

$\Rightarrow$

$Visible \ radiation$

$Wavelength \ of \ radiation \ arising \ from \ two \ close \ energy \ levels \ in \ . hydrogen$

$Rightarrow$

$Microwave$ .

Out of the following options which one can be used to produce a propagating electromagnetic wave?

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A charge moving at constant velocity
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A stationary charge
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A chargeless particle
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An accelerating charge

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Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
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Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
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Assertion is correct but Reason is incorrect
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Both Assertion and Reason are incorrect

$v_s, v_x$ and

$v_m$ are the speeds of gamma rays X-rays and microwaves respectively in vacuum, then:

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$v_s > v_x > v_m$
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$v_s < v_x < v_m$
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$v_s < v_x > v_m$
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$v_s = v_x = v_m$

Explanation

These all above mentioned rays are electromagnetic waves and all magnetic waves have same speed in same medium.

The speed of these waves in vacuum are equal to each other and to the speed of light in vacuum.

$v_s=v_x=v_m=c_0$

The frequency order for X-rays(A),

$\gamma$ rays(B), UV rays(C) is

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$B>A>C$
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$A>B>C$
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$C>B>A$
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$A>C>B$

Displacement current is continuous:

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when electric field is changing in the circuit
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when magnetic field is changing in the circuit
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in both types of fields
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through wires and resistance only

Which of the following waves is used in Raman spectroscopy?

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UV
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$x-$ rays
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$\gamma-$ rays
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IR

Which of the following rays is emitted by a human body?

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x-rays
0%
visible rays
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uvrays
0%
IR rays
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none of these

Speed of electromagnetic waves is the same:

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for all wavelengths
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in all media
0%
for all intensities
0%
for all frequencies

Explanation

Speed of electromagnetic waves is dependent upon medium as,

$v=\dfrac{c}{n}$

where

$c$ is the speed of light in vacuum,

$n$ is the refractive index in the medium.

Speed is dependent on wavelength and frequency as

$v=\lambda \nu$

It is independent of intensity.

Infrared radiation was discovered in 1860 by

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William Wallaston
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William Herschel
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William Roentgen
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Thomas Young

Choose the correct answer from the alternatives given.
Displacement current goes through the gap between the plates of a capacitor when the charge of the capacitor

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increases
0%
decreases
0%
increases or decreases
0%
is zero

Explanation

Displacement current inside a capacitor is given by:-

$i_d=\epsilon_0 \dfrac{\phi_E}{dt}$

where

$\phi_E$ is the electric flux inside the capacitor

The displacement current is developed inside a capacitor when there is a change in the electric flux linked with the capacitor. The change in electric flux can occur in both the cases either the charge increases or decreases on the capacitor. This will lead to a change in flux linked with the coil.

Thus, option

$(C)$ is correct.

In case of the electromagnetic waves the angle between the electric and magnetic field vectors is

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$\pi$
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$\pi/2$
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zero
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none of these

The waves relevant to telecommunications are

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visible light
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infrared
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ultraviolet
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microwave

Radio waves of constant amplitude can be generated with

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filter
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rectifier
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FET
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oscillator

Electromagnetic radiation of wave length 0.01 mm belong to ........................ region

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Visible
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Ultraviolet
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Infrared
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None of these

When light propagates in vacuum there is an electric field and a magnetic field. These fields

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are constant in time
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have zero average value
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are perpendicular to the direction of propagation of light.
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are mutually perpendicular

The displacement current flows in the dielectric of a capacitor when the potential difference across its plates

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becomes zero
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has assumed a constant value
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is increasing with time
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is decreasing with time

Which colour of light travels fastest in any medium except air?

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Red
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Violet
0%
Blue
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Orange

Explanation

Red has maximum wavelength and frequency doesn't change while travelling through a medium.

Hence, red will travel the fastest since

$v=f\lambda$

The waves related to tele-communication are

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infrared
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visible light
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microwaves
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ultraviolet rays

Choose the correct answer from the alternatives given.
The conduction current is the same as displacement current when the source is

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AC only
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DC only
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both AC and DC
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neither AC nor for DC

Explanation

For a capacitor, we have:

$Q=CV$

$Q$ is changing, there will be a current in capacitor plates,

$I=dQ/dt=CdV/dt$

when voltage across the capacitor is constant,

$dV/dt=0$

therefore,

$I=0$

It implies that, for a DC (constant ) voltage, the capacitor current is zero. Hence, for a DC source the conduction current and displacement current (capacitor current) are not same.

Whereas, by Maxwell's equation for a time varying voltage (AC voltage), both conduction and displacement currents are same.

The nature of electromagnetic wave is:

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longitudinal
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longitudinal stationary
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transverse
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transverse stationary

Explanation

Electromagnetic waves are transverse. The are moving with a certain phase velocity

$v=\dfrac{\omega}{k}$ . Thus they are not stationary.

The frequency from

$3\times { 10 }^{ 9 }Hz$ to

$3\times { 10 }^{ 10 }Hz$ is

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high frequency band
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super high frequency band
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ultra high frequency band
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very high frequency band

Identify the most notable difference between a ultraviolet wave and a light wave ?

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Speed
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Refractive index
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Reflectivity
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Amplitude
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Frequency

Select wrong statement from the following:
Electromagnetic waves

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are transverse
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travel with same speed in all media
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travel with the speed of light
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are produced by accelerating charge

Explanation

Electromagnetic waves are transverse and do not need a material medium to travel.
The speed of all electromagnetic waves is equal to the speed of light. In fact this let to the conclusion that light is an electromagnetic wave.

Accelerating charge particles produce electromagnetic waves.

However the speed of electromagnetic waves changes with media as

$v=\dfrac{c}{n}$

where n is the refractive index of the given medium.

Electromagnetic waves do not transport

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energy
0%
charge
0%
momentum
0%
information

Explanation

Waves carry energy.

Since it carries energy, it must have some momentum, which is given as

$p=\dfrac{h}{c}$

Energy is a form of information. Hence it is carried by a wave.

Out of the following , whose velocity is equal to that of light?

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of $\beta$ rays
0%
of sound waves
0%
of ultrasonic waves
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none of these

Name the seven prominent colours of the white light spectrum in order of their increasing frequencies

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Violet, Indigo, Blue, Green, Yellow, Orange, Red
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Red, Orange, Yellow, Green, Blue, Indigo, Violet
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Red, Orange, Violet, Yellow, Green, Blue, Indigo
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Orange, Yellow, Green, Red, Blue, Indigo, Violet

Write the approximate wavelengths for red light.

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$1000A^o$
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$2000A^o$
0%
$4000A^o$
0%
$8000A^o$

Explanation

The range of wavelength for red is

$6200-7500$

$A^o$

What is the range of wavelength of the spectrum of white light in

$A^o$ ?

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$4000A^o$ to $5000A^o$
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$5000A^o$ to $6000A^o$
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$6000A^o$ to $8000A^o$
0%
All the above

Explanation

The range of wavelength of visible light is approximately

$4000-8000$

$A^o$ , with violet being at the lower end (

$3800-4500$

$A^o$ ) and red at the higher end (

$6200-7500$

$A^o$ ).

Write the approximate wavelengths for blue light?

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$800A^o$
0%
$1600A^o$
0%
$3200A^o$
0%
$4800A^o$

Explanation

The range of wavelengths for blue is

$4500-4950$

$A^o$ .

A wave has wavelength

$50A^o$ . Name the wave.

0%
X-ray
0%
Gamma ray
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Radio waves
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Micro waves

Explanation

Electromagnetic radiation is classified into types according to the frequency of the wave. These types include, in order of increasing frequency, radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.
The frequency is the inverse of wavelength. Hence, in the order of increasing wavelength, the waves are Gamma rays (

$<1nm$ ), X-rays (

$1-10nm$ ), infra red rays (

$700-{ 10 }^{ 5 }nm$ ), micro waves (

${ 10 }^{ 5 }-{ 10 }^{ 8 }nm$ ), radio waves (

${ >10 }^{ 8 }nm$ ).
Therefore, X-rays has a wavelength of

$50 \mathring{A}$ .

Which radiation is used for satellite communication?

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Micro waves
0%
X rays
0%
Gamma rays
0%
Infra red rays

The wavelengths for the light of red and blue colours are roughly

$7.8\times 10^{-7}m$ and

$4.8\times 10^{-7}m$ respectively. Which colour has the greater speed in glass?

0%
Red light
0%
Violet light
0%
Yellow light
0%
All colors have same speed

Explanation

When travelling through a medium, the frequency of light doesn't change. Hence, red light having the maximum wavelength will travel fastest through glass as speed of light is given by

$v=f\lambda$ where;

$f$ is the frequency and

$\lambda$ is the wavelength of light travelling at speed

$v$ .

What is the range of wavelength of the spectrum of white light in

$nm$ ?

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$400nm$ to $500nm$
0%
$500nm$ to $600nm$
0%
$600nm$ to $800nm$
0%
All the above

Explanation

The range of wavelength of visible light is approximately

$400-800 nm$ with violet being at the lower end (

$380-450 nm$ ) and red at the higher end (

$620-750 nm$ ).

Name color/s of the spectrum of white light which have wavelength longer than blue light.

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Green
0%
Yellow
0%
Red
0%
All the above

Name the rays or waves of wavelength nearly

$0.1nm$ .

0%
IR rays
0%
UV rays
0%
Gamma rays
0%
X-rays

Explanation

X-rays is a form of electromagnetic radiation. Most X-rays have a wavelength ranging from

$0.01$ to

$10$ nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz (

${ { 3\times 10 }^{ 16 }\ Hz\ to\ 3\times 10 }^{ 19 }Hz$ ) and energies in the range 100 eV to 100 keV.
Hence, the rays or waves of $0.1 nm$ is X-rays.

Name the region beyond the red end of the spectrum.

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Ultra red
0%
infra red
0%
dark red
0%
light red

The most energetic electromagnetic radiations are:

0%
microwaves
0%
ultraviolet waves
0%
$X$ -rays
0%
gamma rays

Name the high energetic invisible electromagnetic wave which helps in the study of structure of crystals.

0%
$X$ -rays
0%
Cathod rays
0%
Gamma rays
0%
All of the above

CBSE Questions for Class 12 Medical Physics Electromagnetic Waves Quiz 1 - MCQExams.com

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Practice Class 12 Medical Physics Quiz Questions and Answers

CBSE Questions for Class 12 Medical Physics Electromagnetic Waves Quiz 1 - MCQExams.com

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Practice Class 12 Medical Physics Quiz Questions and Answers

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