CBSE Questions for Class 12 Medical Physics Electromagnetic Waves Quiz 8 - MCQExams.com

The correct sequence of various regions in absorption spectrum is?
  • Ultraviolet, visible, infra-red, microwave
  • Microwave, visible, infra-red, X-rays
  • Infra-red, gamma rays, ultraviolet, microwave
  • Visible, ultraviolet, microwave, infra-red
Choose the correct answer from the alternatives given.
A plane electromagnetic wave of frequency $$25 MHz$$ travels in free space along $$X$$-direction. At a particular point in space and time, electric field $$\vec E=6.3\ \hat j\ V/m$$. What is $$B$$ at this point.
  • $$1.2 \, \times \, 10^{-6} \, T$$
  • $$1.2 \, \times \, 10^{-8} \, T$$
  • $$2.1 \, \times \, 10^{-6} \, T$$
  • $$2.1 \, \times \, 10^{-8} \, T$$

A microwave and an ultrasonic sound wave have the same wavelength. Their frequencies are in the ratio (approximately) 
  • $$10^2$$
  • $$10^4$$
  • $$10^6$$
  • $$10^8$$
The ultra-high frequency band of radio waves in electromagnetic wave is used as in:
  • television waves
  • cellular phone communication
  • commercial FM radio
  • both (a) and (c)
Choose the correct answer from the alternatives given.
Which of the following is not true for electromagnetic waves?
  • They transport energy.
  • They have momentum.
  • They travel at different speeds in air depending on their frequency.
  • They travel at different speeds in medium depending on their frequency.
Choose the correct answer from the alternatives given.
Suppose that the electric field amplitude of an electromagnetic wave propagating along x-direction is $$E_0$$ = 120 N $$C^{-1}$$ and that frequency is: $$\upsilon$$ = 50.0 MHz.
  • The expression of elctric field is $$ \vec{E} = 120sin \left ( \dfrac{\pi}{3}x-100\pi \times10^6t \right )\hat{j}$$
  • The expression of electric field is $$ \vec{E} = 60sin \left ( \dfrac{\pi}{3}x-100\pi \times10^6t \right )\hat{j}$$
  • the expression of magnetic field is $$ \vec{B} = 40\times10^{-8}sin \left ( \dfrac{\pi}{3}x-\pi \times10^8t \right )\hat{k}$$
  • Both (a) and (c)
The electric field of an electromagnetic wave traveling through the vacuum is given by the equation $$E=E_0\ sin (Kx-\omega t).$$ The quantity that is independent of wavelength is:
  • $$k\omega$$
  • $$\dfrac{k}{\omega}$$
  • $$k^2\omega$$
  • $$\omega$$
Choose the correct answer from the alternatives given.
A radio can tune to any station in 7.5 MHz to 12 MHz band. The corresponding wavelength band is
  • 40 m to 25 m
  • 30 m to 25 m
  • 25 m to 10 m
  • 10 m to 5 m
Which of the following electromagnetic wave is used in high precision application like LASIK eye surgery?
  • Microwave
  • Ultraviolet rays
  • Gamma rays
  • X-rays
Which of the following electromagnetic wave play an important role in maintaining the earths warmth or average temperature through the greenhouse effect? 
  • Visible rays
  • Infrared waves
  • Gamma rays
  • Ultraviolet rays
Which of the following electromagnetic waves is used in medicine to destroy cancer cells?
  • IR-rays
  • Visible rays
  • Gamma rays
  • Ultraviolet rays
Maxwell in his famous equations of electromagnetism, introduced the concept of
  • ac current
  • displacement current
  • impedance
  • reactance
Choose the correct answer from alternatives given.
The phenomena involved in the reflection of radio waves by ionosphere is similar to
  • reflection of light by a plane mirror.
  • total internal reflection of light in air during a mirage.
  • dispersion of light by water molecules during the formation of a rainbow.
  • scattering of light by the particles of air.
An electromagnetic wave radiates outwards from a dipole antenna, with $$E_0$$ as the amplitude of its electric field vector. The electric field $$B_0$$ which transports significant energy from the source falls off as
  • $$\dfrac{1}{r^3}$$
  • $$\dfrac{1}{r^2}$$
  • $$\dfrac{1}{r}$$
  • remains constant.
Which of the following doesnt represent Maxwells equation?
  • $$\oint { \overrightarrow { E } .\bar { dA } = } \dfrac { q }{ { \varepsilon }_{ 0 } } $$
  • $$\oint { \overrightarrow { B } .\bar { dA } = } 0$$
  • $$\oint { \overrightarrow { E } .\bar { dl } =\dfrac { -dB }{ dt } } $$
  • $$\oint { \overrightarrow { B } .\bar { dl } = } { \mu }_{ 0 }{ I }_{ C }+{ \mu }_{ 0 }{ \varepsilon }_{ 0 }\dfrac { d{ \phi }_{ E } }{ dt } $$
An electromagnetic waves can be produced, when charge is 
  • Moving with constant velocity
  • Moving in a circular orbit
  • Falling in an electric field
  • both (b) and (c)
The charge on a parallel plate capacitor varies as $$q = {q}_{0}cos2vt$$. The plates are very large and close together  (area = A, separation = d ) , the displacement current through the capacitor is
  • $${q}_{0}2v sinvt$$
  • $$-{q}_{0}2v sinvt$$
  • $${q}_{0}2 sinvt$$
  • $${q}_{0}v sinvt$$
A plane electromagnetic wave travels in a vacuum in the z-direction. If the frequency of the wave is 40 MHz, then its wavelength is:
  • $$5\ m$$
  • $$7.5\ m$$
  • $$8.5\ m$$
  • $$10\ m$$
The matter-wave picture of electromagnetic wave/radiation elegantly incorporated the:
  • Heinsenbergs uncertainty principle
  • correspondence principle
  • cosmic theory
  • Hertzs observations
The ratio of contributions made by the electric field and magnetic field components to the intensity of an electromagnetic wave is:
  • $$c : 1$$
  • $$c^2: 1$$
  • $$1 : 1$$
  • $$\sqrt{c} : 1$$
The part of the spectrum of electromagnetic radiation used to cook food is
  • Ultraviolet rays
  • Cosmic rays
  • X rays
  • Microwaves
An electromagnetic wave of frequency $$\upsilon = 3$$ MHz passes from a vacuum into a dielectric medium with permittivity $$ = 4$$, Then
  • Wavelength and frequency both become half.
  • Wavelength is doubled and frequency remains unchanged.
  • Wavelength and frequency both remains unchanged.
  • Wavelength is halfved and frequency remains unchanged.
Which of the following is not true for electromagnetic waves?
  • They transport energy.
  • They have momentum.
  • They travel at different speeds in air depending on their frequency.
  • They travel at different speeds in medium depending on their frequency.
Which of the following ray is not electromagnetic wave?
  • X-rays
  • $$\gamma$$-rays
  • $$\beta$$-rays
  • Heat rays
The amplitude of the magnetic field of a harmonic electromagnetic wave in vacuum is $${B}_{0}$$ = 510 nT. The amplitude of the electric field part of the wave is
  • 120 N $${C}^{-1}$$
  • 163 N $${C}^{-1}$$
  • 510 N $${C}^{-1}$$
  • 153 N $${C}^{-1}$$
The rms value of the electric field of the light coming from sun is 720 N $$C^{-1}$$. The average total energy density of the electromagnetic wave is
  • $$3.3 10^{-3} J m^{-3}$$
  • $$4.58 10^{-6} J m^{-3}$$
  • $$6.37 10^{-9} J m^{-3}$$
  • $$81.35 10^{-12} J m^{-3}$$
Which one of the following is a property of a monochromatic, plane electromagnetic wave in free space?
  • Electric and magnetic fields have a phase difference of $${\pi}/{2}$$
  • The energy contribution of both electric and magnetic fields are equal
  • The direction of propagation is in the direction of $$\overline { B } \times \overline { E } $$
  • The pressure exerted by the wave is the product of its speed and energy density.
The ultra high frequency band of radiowaves in electromagnetic waves is used as in
  • Television waves
  • Cellular phone communication
  • Commercial FM radio
  • Both (b) and (c)
A plane electromagnetic wave propagating along x direction can have the following pairs of $$\overrightarrow { E }$$ and $$\overrightarrow { B }$$.
  • $${ E }_{ y },{ B }_{ z }$$
  • $${ E }_{ z },{ B }_{ y }$$
  • $${ E }_{ x },{ B }_{ y }$$
  • both (a) and (b)
Which of the following electromagnetic wave play an important role in maintaining the earths warmth or average temperature through the green house effect?
  • Visible rays
  • Infrared rays
  • Gamma rays
  • Ultraviolet rays
An electromagnetic wave radiates outwards from a dipole antenna, with $${ E }_{ 0 }$$ as the amplitude of its electric field vector. The electric field $${ E }_{ 0 }$$ which transports significant energy from the source falls off as
  • $$\dfrac { 1 }{ { r }^{ 3 } }$$
  • $$\dfrac { 1 }{ { r }^{ 2 } }$$
  • $$\dfrac { 1 }{ { r }}$$
  • remains constant.
The decreasing order of wavelength of infrared, microwave, ultraviolet and gamma rays is
  • Microwaves, Infrared, ultraviolet, gamma rays.
  • Infrared, Microwaves, ultraviolet, gamma rays.
  • ultraviolet, gamma rays, Infrared, Microwaves
  • Microwaves, gamma rays, Infrared, ultraviolet
An electromagnetic radiation has an energy of 13.2 KeV. Then the radiation belongs to the region of
  • Visible light
  • Ultraviolet light
  • Infrared
  • X-ray
One requires 2 IeV of energy to dissociate a carbon molecule into carbon and oxygen atoms. The minimum frequency of the appropriate electromagnetic radiation to achieve the dis-acceleration lines is 
  • visible region
  • interacted region
  • ultraviolet region
  • microwave region
A. wavelength of microwave is greater than that of ultraviolet rays.
B. The wave length of infrared rays is lesser than that of ultraviolet rays.
C. wavelength of microwave is lesser than that of ultraviolet rays
D. Gamma rays has shortest wavelength in the electromagnetic spectrum.
Choose the correct option from the given options.
  • A and B are true
  • B and C are true
  • C and D are true
  • A and D are true
Photons of an electromagneitc radiation has an energy $$11keV$$ each. To which region of electromagnetic spectrum does it belong?
  • $$X-ray\ region$$
  • $$Ultra\ violet\ region$$
  • $$infrared\ region$$
  • $$visible\ region$$
Radio waves of constant amplitude can be generated with:
  • Filter
  • Rectifier
  • FET
  • Oscillator
The operating voltage in coolidge tube is $${10}^{5}V$$. The speed of X-Rays produced is ________ $$m{s}^{-1}$$
  • $$2\times { 10 }^{ 8 }\quad $$
  • $${ 10 }^{ 6 }$$
  • $${ 10 }^{ 5 }$$
  • $$3\times { 10 }^{ 8 }$$
A beam of ultraviolet light of all wavelengths passes through hydrogen gas at room temperature, in the $$x-$$direction. Assume that all photons emitted due to electron transitions inside the gas emerge in the $$y-$$direction. Let $$A$$ and $$B$$ denote the lights emerging from the gas in the $$x-$$ and $$y-$$directions respectively. Then,
  • some of the incident wavelengths will be absent in $$A$$
  • only those wavelengths will be present in $$B$$ which are absent in $$A$$
  • $$B$$ will contain some visible light
  • $$B$$ will contain some infrared light
If a source of power $$4$$ kW produces $$10^{26}$$ photons/second, the radiation belongs to a part of the spectrum called:
  • X-rays
  • Ultraviolet rays
  • Microwaves
  • $$\gamma$$-rays
A radiation of energy E falls normally on a perfectly reflecting surface. The momentum transferred to the surface is:
  • $$\dfrac{E}{c}$$
  • $$\dfrac{2E}{c}$$
  • $$Ec$$
  • $$\dfrac{E}{c^2}$$
The intensity of sun on earth is $$1400 W/m^2$$. Assuming earth to be a black body. Calculate radiation pressure?
  • $$4.66 \times 10^6 N/m^2$$
  • $$1.4 \times 10^{-6} N/m^2$$
  • $$4.66 \times 10^{-6} N/m^2$$
  • $$7 \times 10^{-6} N/m^2$$
A parallel plate capacitor with circular plates of radius $$R$$ is being charged as shown. At the instant shown, the displacement current in the region between the plates enclosed between $$\cfrac{R}{2}$$ and $$R$$ is given by
1022452_f9249be23b364304adb093ef4715dfa4.PNG
  • $$\cfrac{3}{4}i$$
  • $$\cfrac{1}{4}i$$
  • $$3i$$
  • $$\cfrac{4}{3}i$$
The electric field associated with an e.m. wave in vacuum is given by $$\vec {E} = 40\cos (kz - 6\times 10^{8}t)\hat {i}$$, where $$E, z$$ and $$t$$ in $$volt/m$$, meter and seconds respectively. The value of wave vector $$k$$ is
  • $$6m^{-1}$$
  • $$3m^{-1}$$
  • $$2m^{-1}$$
  • $$0.5m^{-1}$$
The electric field part of an electromagnetic wave in a medium is represented by $$Ex=0$$

$$Ey= 2.5 N/C ((2*10^6 rad/m)t - (*10^-2 rad/s) x)$$

$$Ez=0$$ the wave is
  • Moving along X direction with frequency 10^6 Hz and wavelength 100m
  • Moving along X direction with frequency 10^6 Hz and wavelength 200m
  • Moving along - X direction with frequency 10^6 Hz and wavelength 100m
  • Moving along y direction with frequency 2*10^6 Hz and lwavelength 100m
The x -ray beam coming from an x - ray tube will be 
  • Monochromatic
  • Having all wavelengths smaller than a certain maximum wavelength
  • Having all wavelengths larger than a certain minimum wavelength
  • Having all wavelengths lying between a minimum and a maximum wavelength
Displacement current goes through the gap between the plates of a capaitor when the charge of the capacitor:
(i) does not change
(ii) change with time
(iii) increases
 (iv) decreases
  • ( i ), ( iii ) and ( iv )
  • ( i ), and ( ii ) and ( iv )
  • ( ii ), ( iii ) and ( iv )
  • ( i ), ( ii ) and ( iii )
The velocity of light is $$3.0 \times {10^8}m{s^{ - 1}}$$. Which value is closest to the wavelength in nanometres of a quantum of light with frequency of $$8 \times {10^{15}}{s^{ - 1}}$$?
  • $$3 \times {10^7}$$
  • $$2 \times {10^{ - 25}}$$
  • $$5 \times {10^{ - 18}}$$
  • $$3.7 \times {10^1}$$
A parallel plate condenser consists of two circular plates each of radius $$2cm$$ separated by a distance of $$0.1mm$$. A time varying potential difference of $$5\times {10}^{13}v/s$$ is applied across the plates of the condenser. The displacement current is:
  • $$5.50A$$
  • $$5.56\times {10}^{2}A$$
  • $$5.56\times {10}^{3}A$$
  • $$2.28\times {10}^{4}A$$
A plane electromagnetic wave of frequency $$28MHz$$ travels in free space along the positive x-direction. At a particular point in space and time, electric field is $$9.3V/m$$ along positive y-direction. The magnetic field (in T) at that point is 
  • $$3.1\times10^{-8} $$ along positive z-direction
  • $$3.1\times10^{-8} $$ along negative z-direction
  • $$3.2\times10^{7} $$ along positive z-direction
  • $$3.2\times10^{7} $$ along negative z-direction
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