CBSE Questions for Class 12 Medical Physics Electromagnetic Waves Quiz 9 - MCQExams.com

Which of the following represents an infra-red wavelength?
  • $$10^{-4}cm$$
  • $$10^{-5}cm$$
  • $$10^{-6}cm$$
  • $$10^{-7}cm$$
What is the wavelength range of visible light?
  • $$ 4 \times 10^{-7} m $$ to $$ 8 \times 10^{-7} m$$
  • $$ 4 \times 10^{-9} m $$ to $$ 8 \times 10^{-9} m$$
  • $$ 4 \times 10^{-5} m $$ to $$ 8 \times 10^{-5} m$$
  • $$ 4 \times 10^{-6} m $$ to $$ 8 \times 10^{-6} m$$
Electromagnetic wave of intensity $$1400\ W/m^{2}$$ falls on metal surface on area $$1.5\ m^{2}$$ is completely absorbed by it. Find out force exerted by beam.
  • $$14\times 10^{-5}N$$
  • $$14\times 10^{-6}N$$
  • $$7\times 10^{-5}N$$
  • $$7\times 10^{-6}N$$
At a particular instant, the current in the circuit given below is i. The displacement current between the plates of the capacitor shown below is
1114542_d59e19c9f7514a5ab6059c33c3ab43a6.png
  • Zero
  • i
  • $$\frac{i}{2}$$
  • $$\frac{i}{4}$$
The magnetic field in a plane electromagnetic wave is given by $$=2\times10^{-7} \sin(0.5\times 10^3 x+1.5\times10^{11}t)$$. This electromagnetic wave is
  • Visible light
  • Infrared
  • Microwave
  • Radiowave
What is the wavelength of the wave whose frequency is $$10^{12}Hz$$? 
  • 0.3
  • 0.4
  • 0.5
  • 0.6
What is the type of invisible radiation from space that can be detected from Earth's surface?
  • Gamma rays
  • X-rays
  • Infrared radiation
  • Radio waves
A parallel plate condenser of capacity $$1 nF$$ is connected to a battery of emf $$2v$$ though a resistance of $$1M \Omega$$. The displacement current after $$10^{-3}\ \sec$$ is:
  • $$0.37\ \mu\ A$$
  • $$0.74\ \mu\ A$$
  • $$1.48\ \mu\ A$$
  • $$0.175\ \mu\ A$$
Mark the correct option in impure spectrum :
  • Order of colours is reverse
  • Order of colours is irregular
  • colours are overlapped
  • no colours is present
A parallel plate condenser has circular plates$$,$$ each of radius $$5cm.$$ It is being charged so that electric field in the gap between its plates rises steadily at the rate of $${10^{12}}V/ms.$$  What is the displacement current$$?$$ 
  • $$0.07 A$$
  • $$1.39 A$$
  • $$13.9 A$$
  • $$139 A$$
An electromagnetic wave travels along z-axis. which of the following pairs of space and time varying fields would generate such a wave.
  • $${E_{X,}}{B_Y}$$
  • $${E_{Y,}}{B_X}$$
  • $${E_{Z,}}{B_X}$$
  • $${E_{Y,}}{B_Z}$$
An ultrasound equipment work at frequency:
  •  Higher than $$20,000 Hz $$
  •  Higher than $$10,000 Hz $$
  •  Lower than 4420,000 Hz $$
  •  Lower than $$10,000 H_2 $$
A metal block is exposed to beams of X-ray of different wavelength. X-rays of which wavelength penetrate most?
  • $$2\overset{o}{A}$$
  • $$4\overset{o}{A}$$
  • $$6\overset{o}{A}$$
  • $$8\overset{o}{A}$$
If electric field in a non-magnetic medium for EM wave is given by $$\vec{ E } =100 \sin\left( 10^ 8\quad t\quad +2z \right) \hat { j }$$ then $$\vec {H}$$ is.
  • $$ \dfrac { 50 }{ \pi } sin\left( 10^ 8\quad t\quad +\quad 2z \right) \hat { i } $$
  • $$ \dfrac { 5 }{ 6\pi } sin\left( 10^ 8\quad t\quad +\quad 2z \right) \hat { i } $$
  • $$ 20 sin\left( 10^ 8\quad t\quad +\quad 2z \right) \hat { i } $$
  • $$ \dfrac { 25 }{ \pi } sin\left( 10^ 8\quad t\quad +\quad 2z \right) \hat { j } $$
Pick out the statement which is not true
  • IR radiatins are used for long distance photogtaphy
  • IR radiatins arise due to inner electon transitions in atoms
  • IR radiations are detected by using a bolometer
  • Sun is the natural source of IR radiation
Select the correct statement from the following
  • Electromagnetic waves cannot travel in vaccum
  • Electromagnetic waves are longitudinal waves
  • Electromagnetic waves are produced by charges moving with uniform velocity.
  • Electromagnetic waves carry both energy and momentum as they propagate through space.
If $$P$$ represents radiation pressure, $$c$$ represents speed of lights and $$l$$ represents radiation energy striking a unit area per second, then non -zero integers $$x,y$$ and $$z$$ such that $$P^ xl^ yc^z$$ is dimensionless are
  • $$x=0, y=0, z=0$$
  • $$x=1, y=-1, z=1$$
  • $$x=-1, y=1, z=1$$
  • $$x=1, y=1, z=1$$
The longitudinal waves having frequency above 20 $$\mathrm { kHz }$$ are called
  • Infrasonic waves
  • Audible waves
  • Ultrasonic waves
  • Shock waves
The displacement current flows in a dielectric of a capacitor when the potential difference across its plates:
  • Has assumed constant value
  • Is decreasing with time
  • Is increasing with position
  • is zero
Which of the following have zero average value in a plane electromagnetic wave?
(i) Magnetic field
(ii) Electric field
(iii) Electric energy
(iv) Magnetic energy.
  • (i) and (ii)
  • (i) and (iv)
  • (ii) and (iii)
  • (iii) and (iv)
The infra-red spectrum lies between:
  • radio wave and micro-wave region
  • the micro-wave and visible region
  • the visible and ultra violet region
  • the ultra violet and the X-ray region
In Maxwell's velocity distribution curve area under the graph 
  • Increases when temperature is increased
  • Deccreases when temperature is increased
  • Remains same at all temperature
  • Depends on the pressure of the gas
Frequency ranges for micro waves are :
  • $$3\times { 10 }^{ 9 }\quad to\quad 3\times { 10 }^{ 4 }Hz$$
  • $$3\times { 10 }^{ 13 }\quad to\quad 3\times { 10 }^{ 9 }Hz$$
  • $$3\times { 10 }^{ 14 }\quad to\quad 3\times { 10 }^{ 9 }Hz$$
  • $$3\times { 10 }^{ 11 }\quad to\quad 3\times { 10 }^{ 9 }Hz$$
Which of the following has maximum energy ?
  • radio waves
  • X rays
  • light waves
  • micro waves
X - ray beam can be deflected by 
  • Magnetic field
  • Electric field
  • Both (a) & (b)
  • None of these
The displacement current was named as current because
  • It is similar conduction current
  • It produced a magnetic field
  • It is a time varying field
  • It is current due to uniformly moving charge
Which one of the following is the primary effect of UV radiation caused due to depletion of ozone layer?
  • Heart attack
  • Skin cancer
  • High fever
  • All of these
  • None of these
An object is placed at some distance from a radio station. If the interval between transmission and reception of pulses is $$2.66\times 10^{-2}$$ sec, then the distance is?
  • $$4000$$ km
  • $$2000$$ km
  • $$3000$$ km
  • $$2500$$ km
The wavelength of a radio wave of frequency of $$1$$ MHz is?
  • $$400$$ m
  • $$300$$ m
  • $$350$$ m
  • $$200$$ m
Assertion :- Microwave communication is preferred over optical communication. 
Reason :- Microwaves provide large number of channels and band width compared to optical signals. 

  • Both assertion and reason are true and the reason is correct explanation of assertion.

  • Both assertion and reason are true and the reason is not the correct explanation of assertion.

  • Assertion is true but reason is false.
  •  Both assertion and reason are false.
When ultraviolet rays incident on metal plate then photoelectric effect does not occure, it occursby incidence of
  • Infrared rays
  • X-rays
  • Radio wave
  • Green house effect
For an electromagnetic radiation,
  • only momentum is quantised
  • only energy is quantised
  • both energy and momentum are
    quantised
  • neither of them is quantised
Which one among the following waves are waves of heat energy?
  • Radiowaves
  • Infrared waves
  • Ultraviolet waves
  • Microwaves
Electromagnetic waves are :
  • Transverse waves
  • Longitudinal waves
  • Neither longitudinal nor transverse
  • Stationary waves
The radio waves of frequency 30 MHz to 300 MHz belong to:
  • high frequency band
  • very high frequency band
  • ultra high frequency band
  • super high frequency band.
A parallel plate capacitor of plate separation 2 mm is connected in an electric circuit having source voltageWhat is the value of the displacement current for $$10^{-6}$$ s, if plate area is 60 $$cm^2$$
  • $$1.062 \times 10^{-2} \ A$$
  • $$2.062 \times 10^{-2} \ A$$
  • $$3.062 \times 10^{-2} \ A$$
  • $$5.062 \times 10^{-2} \ A$$
Which wavelength of harmful UV-radiations is prevented by ozone layer in entering the Earth atmosphere?
  • $$210-300nm$$
  • $$200-310nm$$
  • $$120-210nm$$
  • $$400-700nm$$
Which one of the following is not a electromagnetic waves?
  • X - rays
  • Gamma rays
  • cathode rays
  • Infrared rays
If the source of power $$4kwW$$ produces $$10^20$$ photons/second, the radiation belongs to the part of a spectrum called
  • X rays
  • Ultraviolet rays
  • Microwaves
  • Gamma rays
If a source of power $$4\ kW$$ produces $$10^{20}$$ photons/second, the radiation belongs to a part of the spectrum called:-
  • $$\gamma$$-rays
  • $$X$$-rays
  • Ultraviolet rays
  • Microwave

The frequency of the electromagnetic wave, which best suited to observe a particle of the size $$3 \times {10^{ - 6}}{\text{m}}$$ is of the order of:
  • $${10^{14}}{\text{Hz}}$$
  • $${10^{15}}{\text{Hz}}$$
  • $$2 \times {10^{13}}{\text{Hz}}$$
  • $$3 \times {10^{15}}{\text{Hz}}$$
Electro magnetic waves are transverse in nature as is evident by
  • polarization
  • interference
  • reflection
  • deffraction
The following can be arranged in decreasing order of wave number
A. AM radio
B. TV and FM radio
C. Microwave
D. Short radio wave
  • A > B > D > C
  • C > D > B > A
  • A > B > C > D
  • D > C > B > A
M and N are two electromagnetic waves.
The ratio $$\dfrac{wavelength of M}{wavelength of N}=10^5$$. What could M and N be?

MN
AMicrowavesVisible light
BMicrowaves$$\gamma$$-rays
C$$\gamma$$-raysMicrowaves
DVisible lightMicrowaves
  • A
  • B
  • C
  • D
If $$\vec{E} = E_0 \cos (kz) \cos (\omega t)\hat{i}$$ then $$\vec{B}$$ for electromagnetic wave is:
  • $$\vec{B} = \dfrac{E_0}{C} \hat{k}$$
  • $$\vec{B} = \dfrac{E_0}{C} \sin (kz) \sin (\omega t)\hat{i}$$
  • $$\vec{B} = \dfrac{E_0}{C} \sin (kz) \cos (\omega t) \hat{j}$$
  • $$\vec{B} = \dfrac{E_0}{C} \cos (kz) \sin (\omega t) \hat{j}$$
The maximum kinetic energy of electron if wavelength of incident electromagnetic wave is $$260 \,nm$$ and cut-off wavelength is $$380 \,nm$$ given $$hc = 1237 \,nm-eV$$ is
  • $$1.5 \,eV$$
  • $$6.4 \,eV$$
  • $$10 \,eV$$
  • None of these
As its closest approach, the distance between Mars and the Earth is found to be $$60$$ million $$km$$. When the planets are at the closest distance, how long would it take to send a radio message from a space probe of Mars of Earth?
  • $$5\ s$$
  • $$200\ s$$
  • $$0.2\ s$$
  • $$20\ s$$
A welder wears special glasses to protect his eyes mostly from the harmful effect of 
  • Very intense visible light
  • infrared radiation
  • ultraviolet rays
  • microwaves.
The diagram shows the principal regions of the electromagnetic spectrum, with some details labelled. The diagram is not to scale.
What is a typical order of magnitude of the wavelength of the radiation in region Q?

1641902_30c44dfcd7a84436b451b5080dcf808a.png
  • $$10^{-7}$$ m
  • $$10^{-5}$$ m
  • $$10^{-2}$$ m
  • $$10^0$$ m
What is the main type of radiation given out by a campfire?
  • Infra-red
  • Microwave
  • Ultraviolet
  • X-ray
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