Write the Expression for Speed of Electromagnetic Waves in a Medium of Electrical Permittivity ε and Magnetic Permeability μ. - Physics


Write the expression for speed of electromagnetic waves in a medium of electrical permittivity ε and magnetic permeability μ.



The speed of electromagnetic waves (c) is \[c = \frac{1}{\sqrt{\mu\epsilon}}\] where μ is magnetic permeability and ε is electrical permittivity.

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2016-2017 (March) Foreign Set 3

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How are em waves produced by oscillating charges?

Arrange the following electromagnetic wave in the order of their increasing wavelength:

(a) γ- rays

(b) Microwaves

(c) X-rays

(d) Radio waves

Draw a schematic sketch of the electromagnetic waves propagating along the + x-axis. Indicate the directions of the electric and magnetic fields

The amplitude of the magnetic field part of a harmonic electromagnetic wave in vacuum is B0 = 510 nT. What is the amplitude of the electric field part of the wave?

How is the speed of em-waves in vacuum determined by the electric and magnetic field?

In the study of a photoelectric effect the graph between the stopping potential V and frequency v of the incident radiation on two different metals P and Q is shown below:

(i) Which one of the two metals has higher threshold frequency?

(ii) Determine the work function of the metal which has greater value.

(iii) Find the maximum kinetic energy of electron emitted by light of frequency 8 × 1014 Hz for this metal.

Do electromagnetic waves carry energy and momentum ?

What is the ratio of the speed of gamma rays to that of radio waves in a vacuum?

How are electric vector `(vec "E")`, magnetic vector `(vec "B")` and velocity vector `(vec "C")` oriented in an electromagnetic wave?

Which mode of propagation is used by short wave broadcast serves?

In a microwave oven, the food is kept in a plastic container and the microwaves is directed towards the food. The food is cooked without melting or igniting the plastic container. Explain.

A wire carries an alternating current i = i0 sin ωt. Is there an electric field in the vicinity of the wire?

A capacitor is connected to an alternating-current source. Is there a magnetic field between the plates?

Can an electromagnetic wave be polarised?

A plane electromagnetic wave is passing through a region. Consider (a) electric field (b) magnetic field (c) electrical energy in a small volume and (d) magnetic energy in a small volume. Construct the pairs of the quantities that oscillate with equal frequencies.

An electromagnetic wave going through vacuum is described by
E = E0 sin (kx − ωt); B = B0 sin (kx − ωt).
Which of the following equations is true?

Speed of electromagnetic waves is the same

A point charge is moving along a straight line with a constant velocity v. Consider a small area A perpendicular to the motion of the charge. Calculate the displacement current through the area when its distance from the charge is x. The value of x is not large, so that the electric field at any instant is essentially given by Coulomb's law.

The energy associated with light of which of the following colours is minimum : 

This is an example of step-up transformer .

Define frequency modulation and state any one advantage of frequency modulation (FM) over amplitude modulation (AM). 

State any one property which is common to all electromagnetic waves.

The energy levels of an atom of a certain element are shown in the given figure. Which one of the transitions A, B, C, D or E will result in the emission of photons of electromagnetic radiation of wavelength 618.75 nm? Support your answer with mathematical calculations.

Which of the following electromagnetic radiations is used for viewing objects through fog ______.

An e.m. wave is propagating in a medium with a velocity `vec"v" = "v" hat"i"`. The instantaneous oscillating electric field of this e.m. wave is along +y-axis, then the direction of an oscillating magnetic field of the e.m. wave will be along:

Which one of them is used to produce a propagating electromagnetic wave?

The electric and magnetic fields of an electromagnetic wave are ______.

What is displacement current?

What are electromagnetic waves?

Write notes on Ampere-Maxwell law.

Write a short note on the radio waves.

Discuss the Hertz experiment.

A transmitter consists of LC circuit with an inductance of 1 μH and a capacitance of 1 μF. What is the wavelength of the electromagnetic waves it emits?

Maxwell’s displacement current is a response to inconsistency in the ______.

Wavelength λ and wave vector k are related by ______.

A man standing on the road has to hold his umbrella at 30° with the vertical to keep the rain away. He throws away the umbrella and starts, running at 10 km/h and finds raindrops hitting his head vertically. The speed of the raindrops with respect to the road is ______.

Which one of the following does not represent simple harmonic motion? Here y denotes the instantaneous displacement. Here, A and B are constants and co is the angular frequency.

A plane electromagnetic wave travels in free space along x-axis. At a particular point in space, the electric field along y-axis is 9.3 Vm−1. The magnetic induction (B) along z-axis is:

Which of the following electromagnetic radiations has the smallest wave length?

Maxwell's equation describe the fundamental law of

If a source is transmitting electromagnetic waves of frequency 8.2 × 106 Hz. then wavelength of electromagnetic waves transmitted from the source will be.

The velocity of light in vacuum can be changed by changing

The velocity of electromagnetic wave is parallel to

Which of the following are not electromagnetic waves?

The sun delivers 103w/m2 of electromagnetic flux to the earth's surface. The total power that is incident on a roof of dimension 8m/10m will be

Electromagnetic waves are produced by ______.

Which of the following type of radiations are radiated by an oscillating electric charge?

For a plane electromagnetic wave propagating in x-direction, which one of the following combinations gives the correct possible directions for electric field (E) and magnetic field (B) respectively?

For a plane electromagnetic wave propagating in the x-direction, which one of the following combinations gives the correct possible directions for the electric field (E) and magnetic field (B) respectively?

Even though an electric field E exerts a force qE on a charged particle yet the electric field of an EM wave does not contribute to the radiation pressure (but transfers energy). Explain.

A plane EM wave travelling along z direction is described by `E = E_0 sin (kz - ωt)hati` and `B = B_0 sin (kz - ωt)hatj`. show that 

  1. The average energy density of the wave is given by `u_(av) = 1/4 ε_0E_0^2 + 1/4 B_0^2/mu_0`.
  2. The time averaged intensity of the wave is given by `I_(av) = 1/2 cε_0 E_0^2`.

The intensity of the light from a bulb incident on a surface is 0.22 W/m2 . The amplitude of the magnetic field in this light-wave is ______× 10–9 T. 

(Given: Permittivity of vacuum ε0 = 8.85 × 10–12 C2 N–1 – m–2, speed of light in vacuum c = 3 × 108 ms-1)

A plane electromagnetic wave of frequency 500 MHz is travelling in a vacuum along a y-direction.

At a particular point in space and time, `vec"B"` = 8.0 × 10-8 `hat"Z"`T. The value of the electric field at this point is ______.

(speed of light = 3 × 108 ms-1)

`hat x, hat y, hat z` are unit vectors along x, y, and Z directions.

For an electromagnetic wave travelling in free space, the relation between average energy densities due to electric (Ue) and magnetic (Um) fields is ______.

The electric field in a plane electromagnetic wave is given by `vecE = 200cos[((0.5 xx 10^3)/m)x - (1.5 xx 10^11 "rad"/s xx t)]V/mhatj`. If the wave falls normally on a perfectly reflecting surface having an area of 100 cm2. If the radiation pressure exerted by the E.M. wave on the surface during a 10-minute exposure is `x/10^9 N/m^2`. Find the value of x.

A plane electromagnetic wave travels in free space along the x-direction. The electric field component of the wave at a particular point of space and time is E = 6 Vm-1 along the y-direction. Its corresponding magnetic field component, B would be ______.

Sunlight falls normally on a surface of area 36 cm2 and exerts an average force of 7.2 × 10-9 N within a time period of 20 minutes. Considering a case of complete absorption the energy flux of incident light is ______.

The electric field in an electromagnetic wave is given by E = 56.5 sin ω(t - x/c)Nc-1. Find the intensity of the wave if it is propagating along x-axis in the free space.

(Given ε0 = 8.85 × 10-12 C2 N-1 m-2)

A plane electromagnetic wave with frequency of 30 MHz travels in free space. At particular point in space and time, electric field is 6 V/m. The magnetic field at this point will be x × 10-8 T. The value of x is ______.

An electromagnetic wave of frequency 3 GHz enters a dielectric medium of relative electric permittivity 2.25 from vacuum. The wavelength of this wave in that medium will be ______ × 10-2 cm. 

In a plane electromagnetic wave, the direction of electric field and magnetic field are represented by `hat"k"` and 2`hat"i" - 2hat"j"`, respectively. What is the unit vector along direction of propagation of the wave.

An electromagnetic wave is produced by a charge ______.

Name the electromagnetic wave/radiation which is used to study crystal structure.


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