CBSE Questions for Class 12 Medical Physics Electromagnetic Waves Quiz 7 - MCQExams.com


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  • Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
  • Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
  • Assertion is correct but Reason is incorrect
  • Both Assertion and Reason are incorrect
Who discovered Radio activity?
  • Rutherford
  • Neil's Bohr
  • Einstein
  • Henry Becquerel
The part of the electromagnetic spectrum which is produced by bombarding a metal target with high energy electrons is :
  • Ultraviolet 
  • X-Rays
  • Infrared 
  • Gamma Rays
Hydrogen atom does not emit X-rays because
  • it contains only a single electron
  • energy levels in it are far apart
  • its size is very small
  • energy levels in it are very close to each other
Which one of following have highest frequency?
  • radio waves.
  • infrared.
  • ultraviolet.
  • gamma rays.
Electromagnetic waves that include light belong to
  • light spectrum.
  • electronic spectrum.
  • electromagnet group.
  • electromagnetic spectrum.
If $${\epsilon}_0$$ and $${\mu}_0$$ represent the permittivity and permeability of vaccum and $$\epsilon$$ and $$\mu$$ represent the permittivity and permeability of medium, then refractive index of the medium is given by
  • $$\sqrt{\dfrac{{\epsilon}_0{\mu}_0}{\epsilon \mu}}$$
  • $$\sqrt{\dfrac{\epsilon \mu}{{\epsilon}_0{\mu}_0}}$$
  • $$\sqrt{\dfrac{{\epsilon}_0{\mu}_0}{\epsilon}}$$
  • $$\sqrt{\dfrac{{\epsilon}_0{\mu}_0}{\mu}}$$
In electromagnetic spectrum, the frequencies of $$\gamma$$-rays, X- rays and ultraviolet rays are denoted by $$n_1, n_2$$ and $$n_3$$ respectively then.
  • $$n_1 > n_2 > n_3$$
  • $$n_1 < n_2 < n_3$$
  • $$n_1 > n_2 < n_3$$
  • $$n_1 < n_2 > n_3$$
In electromagnetic wave, according to Maxwell, changing electric field gives.
  • Stationary magnetic field
  • Conduction current
  • Eddy current
  • Displacement current
The working of a microwave oven involves 
  • Absorption of microwaves by matter
  • Reception of microwaves by optical fibre
  • Microwave amplification by stimulated emission of radiation
  • Transmission of microwaves through a metal
The maximum frequency of transmitted radio waves above which the radio waves are no longer reflected back by ionosphere is ................. (N = maximum electron density of ionosphere, g = acceleration due to gravity)
  • $$gN$$
  • $$gN^2$$
  • $$g \sqrt N$$
  • $$g^2N^2$$
Radio waves travel with a speed of.
  • $$3\times 10^8$$ m/sec
  • $$3\times 10^7$$ m/sec
  • $$3\times 10^6$$ m/sec
  • $$3\times 10^9$$ m/sec
White light is passed through a dilute solution of potassium permagnate. The spectrum produced by the emergent light is
  • Band emission spectrum
  • Line emission spectrum
  • Band absorption spectrum
  • Line absorption spectrum
In the spectrum of visible light produced by a prism, dispersion is
  • Uniform throughout the spectrum
  • Maximum in the middle, decreases on either sides
  • Maximum towards yellow
  • Maximum towards violet
Which of the following is not one of the prime health risks associated with greater UV radiation due to the depletion of stratospheric ozone?
  • Increased liver cancer.
  • Increased skin cancer.
  • Reduced immune system
  • Damage to eyes.
The frequencies of X-rays, Gamma rays and visible light waves rays are $$a, b$$ and $$c$$ respectively, then:
  • $$a < b, b > c$$
  • $$a < b, b < c$$
  • $$a > b > c$$
  • $$a > b, b < c$$
The capacity of a parallel plate air capacitor is $$2 \mu F$$ and voltage between the plates is changing at the rate of $$3 {V}/{S}$$. The displacement current in the capacitor is:
  • $$2 \mu F$$
  • $$3 \mu F$$
  • $$5 \mu F$$
  • $$6 \mu F$$
IR region lies between.
  • Radio waves and microwave regions
  • Microwave and visible
  • Visible and UV region
  • UV rays and X-ray region
Which of the following has zero average value in a plane electromagnetic wave?
  • Kinetic energy
  • Magnetic field
  • Electric field
  • Both (b) and (c)
Find the mismatch
  • Sky wave communication : Frequency upto 30 MHz
  • Line-of-sight communication : Frequency greater than 40 MHz
  • Mobile telephony : Frequency range 800-950 kHz
  • Facsimile : Static document
  • Ground wave propagation : Frequency less than a few MHz
The ionospheric layer acts as a reflector for the frequency range 
  • 1 kHz to 10 kHz
  • 3 to 30 MHz
  • 3 to 30 kHz
  • 100 kHz to 1 MHz
  • 3 GHz to 30 GHz
Light is an electromagnetic wave. Its speed in vacuum is given by the expression
  • $$\displaystyle \sqrt { { \mu }_{ 0 }{ \varepsilon }_{ 0 } } $$
  • $$\displaystyle \sqrt { \frac { { \mu }_{ 0 } }{ { \varepsilon }_{ 0 } } } $$
  • $$\displaystyle \sqrt { \frac { { \varepsilon }_{ 0 } }{ { \mu }_{ 0 } } } $$
  • $$\displaystyle \frac { 1 }{ \sqrt { { \mu }_{ 0 }{ \varepsilon }_{ 0 } } } $$
The waves that are bent down by the ionosphere are
  • Ground waves
  • Surface waves
  • Direct waves
  • Space waves
  • Sky waves
The wavelength of the short radiowaves, micro waves, ultraviolet waves are $${ \lambda  }_{ 1 }, { \lambda  }_{ 2 }$$ and $${ \lambda  }_{ 3 }$$ respectively. Arrange them in decreasing order.
  • $${ \lambda }_{ 1 },{ \lambda }_{ 2 },{ \lambda }_{ 3 }$$
  • $${ \lambda }_{ 1 },{ \lambda }_{ 3 },{ \lambda }_{ 2 }$$
  • $${ \lambda }_{ 3 },{ \lambda }_{ 2 },{ \lambda }_{ 1 }$$
  • $${ \lambda }_{ 2 },{ \lambda }_{ 1 },{ \lambda }_{ 3 }$$
In an electromagnetic wave, the electric magnetising fields are $$100V/m$$ and $$0.265 A/m$$. The maximum energy flow is?
  • $$26.5W/m^2$$
  • $$36.5W/m^2$$
  • $$46.7W/m^2$$
  • $$765W/m^2$$
The atomic number $$(Z)$$ of an element whose $${ k }_{ a }$$ wavelength is $$\lambda $$ is $$11$$. The atomic number of an element whose $${k}_{a}$$, wavelength is $$4\lambda $$ is equal to
  • $$6$$
  • $$11$$
  • $$44$$
  • $$4$$
Electromagnetic waves travel only through.
  • material medium
  • vacuum
  • oscillating electric and magnetic fields
  • oscillating electric and magnetic fields whose directions are perpendicular to each other
The energy of infrared waves is greater than that of
  • Visible light
  • Ultraviolet waves
  • $$X$$-rays
  • Gamma rays
  • Micro waves
A piece of blue glass heated to a high temperature and a piece of red glass at room temperature are taken inside a dimly-lit room. Then.
  • The blue piece will look blue and the red piece will look red as usual
  • The red piece will look brighter red and the blue piece will look ordinary blue
  • The blue will look brighter as compared to the red piece
  • Both the pieces will look equal red
The wavelength of $$X$$-rays is in the range
  • $$0.001\mathring { A } $$ to $$1\mathring { A } $$
  • $$0.001 nm$$ to $$1 nm$$
  • $$0.001 \mu m$$ to $$1 \mu m$$
  • $$0.001 cm $$ to $$1 cm$$
If the distance that a radio wave can travel in the time of one complete cycle is $$10$$ metres, then the frequency of the radio wave in cycles per second is?
  • $$3\times 10^9$$Hz
  • $$3\times 10^6$$Hz
  • $$3\times 10^8$$Hz
  • $$3\times 10^7$$Hz
International broadcasting requires.
  • Medium frequency radio waves
  • High frequency radio waves
  • Low frequency radio waves
  • Longitudinal waves
The transverse nature of electromagnetic radiation is demonstrated by.
  • Interference experiment
  • Diffraction experiment
  • Polarisation experiment
  • Optical activity experiment
Unpolarized light falls first on polarizer $$\left( P \right) $$ and then on analyzer $$\left( A \right) $$. If the intensity of the transmitted light from the analyser is $$\dfrac { 1 }{ 8 }$$th of the incident unpolarized light. What will be the angle between optic axes of $$P$$ and $$A$$?
  • $${ 45 }^{ o }$$
  • $${ 30 }^{ o }$$
  • Zero
  • $${ 60 }^{ o }$$
The sun delivers $$10^3\, Wm^{-2}$$ of electromagnetic flux on the earth's surface. The total power that is incident on a roof of dimensions $$6 \,m \times 30\, m$$ is 
  • $$1.8 \times 10^5\, W$$
  • $$7.2 \times 10^5\, W$$
  • $$0.9 \times 10^5\, W$$
  • $$4.5 \times 10^5\, W$$
Which of the following is correct for X-rays?
  • It has a beam of electrons
  • It is electromagnetic waves
  • It is positively charged particle
  • It is negatively charged particles
 Radiations of intensity $$0.5\ W/m^{2}$$ are striking a metal plate. The pressure on the plate is
  • $$0.166\times 10^{-8} N/m^{2}$$
  • $$0.332\times 10^{-8}N/m^{2}$$
  • $$0.111\times 10^{-8}N/m^{2}$$
  • $$0.083\times 10^{-8}N/m^{2}$$
An electromagnetic wave passing through vacuum is described by the equations. $$E=E_0\sin(kx-\omega t)$$ and $$B=B_0\sin(kx-\omega t)$$. Then.
  • $$E_0k=B_0\omega$$
  • $$E_0\omega =B_0k$$
  • $$E_0B_0=\omega k$$
  • $$E_0=B_0$$
The Electromagnetic wave travelling in a medium has relative permeability $$1.3$$ and relative premittivity $$2.14$$. The speed of EM wave in that medium will be.
  • $$13.6\times 10^6\ m/s$$
  • $$1.8\times 10^6\ m/s$$
  • $$3.6\times 10^8\ m/s$$
  • $$1.8\times 10^8\ m/s$$
Radiation pressure on any surface :
  • is dependent on wavelength of the light used
  • is dependent on nature of surface and intensity of light used
  • is dependent on frequency and nature of surface
  • depends on the nature of source from which light is coming and on nature of surface on which it is falling.
Two monochromatic (wavelength $$=a/5$$) and coherent source of electromagnetic waves are placed on the x-axis at the point $$(2a,0)$$ and $$(-a,0)$$. A detector moves in a circle of radius $$R(>> 2a)$$ whose Centre is at the origin. The number of maximas detected during one circular revolution by the detector are:
  • $$60$$
  • $$15$$
  • $$64$$
  • None
Indigo and red regions of VIBGYOR, respectively fall in the range of wavelength 
  • 430-470 nm and 660-760 nm
  • 300--390 nm and 600-650 nm
  • 390-760 nm and 430-470 nm
  • 660-760 nm and 430-470 nm
The visible part of the electromagnetic spectrum consists of radiations having a wavelength in the range of
  • 400-800 nm
  • 300-2600 nm
  • 390-760 nm
  • 650-760 nm
Frequencies of various radiations are given as
$$f_v\rightarrow$$ Visible light
$$f_r\rightarrow$$ Radio waves
$$f_{UV}\rightarrow$$ Ultra Violet waves
Then which of following is true?
  • $$f_{UV} < f_v < f_r$$
  • $$f_r < f_v < f_{UV}$$
  • $$f_v < f_r < f_{UV}$$
  • $$f_{UV} < f_r < f_v$$
SQUID helps in studying
  • lung cancer
  • heart beats
  • weaker magnetic waves from brain
  • electrical impulses from heart
Choose the correct answer from the alternatives given.
Maxwell in his famouse questions of  eletromagnetism introduce the concept of:
  • ac current
  • displacement current
  • impedance
  • reatance
Study the frequency of the following electromagnetic radiations and select the correct relationship.
$$1$$. Infra red
$$2$$. Microwave
$$3$$. Ultra violet.
  • $$3 > 2 > 1$$
  • $$3 > 1 > 2$$
  • $$1 > 2 > 3$$
  • $$2 > 3 > 1$$
Generation, propagation and detection of electromagnetic waves is the basis of
  • lasers
  • reactors
  • radio and television
  • computer
A long straight cable of lenght $$l$$ is placed symmetrically along z - axis has radius $$a(< < l)$$. The cable consists of a thin wire and a coaxial conducting tube. An alternating current $$I(t) = I_0 sin (2\pi\upsilon t) $$flows down the central thin wire and return along the coaxial conducting tube. The induced electric field at a distance s from the wire inside the cable is $$E(s, t) = \mu_oI_o\upsilon cos(2\pi \upsilon t)\ ln\left (\dfrac{s}{a} \right )\hat{k}$$. The displacement current density inside the cable is 
  • $$ \dfrac{2\pi}{\lambda^2 }I_0 \ ln\left(\dfrac{a}{s}\right )sin(2\pi \upsilon t)\hat{k} $$
  • $$ \dfrac{I}{\lambda^2 }I_0 \, ln \left(\dfrac{a}{s} \right )sin(2\pi \upsilon t)\hat{k} $$
  • $$\dfrac{\pi}{\lambda^2 }I_0 \, ln \left(\dfrac{a}{s} \right )sin(2\pi \upsilon t)\hat{k} $$
  • $$Zero$$
Choose the correct answer from the alternatives given.
Which among the following does not represent Maxwell's equation?
  • $$\phi \, \overset{-}{E}.\overset{-}{dA} \, = \, \dfrac{q}{\varepsilon_0}$$
  • $$\phi \, \overset{-}{B}.\overset{-}{dA} \, = 0$$
  • $$\phi \, \overset{-}{E}.\overset{-}{-dl} \, = \, \dfrac{-dB}{dt}$$
  • $$\phi \, \overset{-}{E}.\overset{-}{dl} \, = \, \mu_0I_C \, + \, \mu_0\varepsilon_0 \, \dfrac{d \phi E}{dt}$$
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