Tamil Nadu Board of Secondary EducationHSC Science Class 12

The dimension of 1μ0∈0 is - Physics


The dimension of `1/(mu_0 ∈_0)` is


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[L2 T-2]

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Chapter 5: Electromagnetic waves - Evaluation [Page 282]


Tamil Nadu Board Samacheer Kalvi Class 12th Physics Volume 1 and 2 Answers Guide
Chapter 5 Electromagnetic waves
Evaluation | Q I. 1. | Page 282


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?

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

A plane electromagnetic wave is travelling through a medium along the +ve z-direction. Depict the electromagnetic wave showing the directions of the oscillating electric and magnetic fields.

 How are the magnitudes of the electric and magnetic fields related to velocity of the em wave?

What are the directions of electric and magnetic field vectors relative to each other and relative to the direction of propagation of electromagnetic waves?

Write the following radiations in ascending order with respect to their frequencies:

X-rays, microwaves, UV rays and radio waves.

Can an electromagnetic wave be deflected by an electric field or a magnetic field?

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

Which of the following have zero average value in a plane electromagnetic wave?
(a) Electric field
(b) Magnetic field
(c) Electric energy
(d) Magnetic energy

The energy contained in a small volume through which an electromagnetic wave is passing oscillates with

A laser beam has intensity 2.5 × 1014 W m−2. Find amplitudes of electric and magnetic fields in the beam.

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.

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?

Give two uses of Microwaves.

Why are e.m. waves non-mechanical?

Write a short note on the visible spectrum.

Explain the Maxwell’s modification of Ampere’s circuital law.

Explain the importance of Maxwell’s correction.

Discuss the source of electromagnetic waves.

A pulse of light of duration 10-6 s is absorbed completely by a small object initially at rest. If the power of the pulse is 60 x 10-3 W, calculate the final momentum of the object.

Let an electromagnetic wave propagate along the x-direction, the magnetic field oscillates at a frequency of 1010 Hz and has an amplitude of 10-5 T, acting along the y – direction. Then, compute the wavelength of the wave. Also write down the expression for the electric field in this case.

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 ______.

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?

An accelerate electron would produce.

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 electromagnetic wave is parallel to

Which of the following are not electromagnetic waves?

Dimensions of ε0 `(d phi_ε)/(dt)` are of

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?

A linearly polarized electromagnetic wave given as E = Eoî cos (kz – ωt) is incident normally on a perfectly reflecting infinite wall at z = a. Assuming that the material of the wall is optically inactive, the reflected wave will be given as ______.

An electromagnetic wave travels in vacuum along z direction: `E = ( E_1hati + E_2hatj ) cos (kz - ωt)`. Choose the correct options from the following:

  1. The associated magnetic field is given as `B = 1/c(E_1hati - E_2hatj) cos (kz - ωt)`.
  2. The associated magnetic field is given as `B = 1/c(E_1hati - E_2hatj) sin (kz - ωt)`.
  3. The given electromagnetic field is circularly polarised.
  4. The given electromagnetic wave is plane polarised.

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 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.

A plane electromagnetic wave, has frequency of 2.0 × 1010 Hz and its energy density is 1.02 × 10-8 J/m3 in vacuum. The amplitude of the magnetic field of the wave is close to `(1/(4piepsilon_0) = 9xx10^9"Nm"^2/"C"^2  "and speed of light" = 3 xx 10^8  "m"  "s"^-1)`:

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 ______.

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.

A 27 mW laser beam has a cross-sectional area of 10 mm2. The magnitude of the maximum electric field in this electromagnetic wave is given by:

[Given permittivity of space ∈0 = 9 × 10-12 SI units, Speed of light c = 3  108 m/s] 

An electromagnetic wave of frequency v = 3.0 MHz passes from vacuum into a dielectric medium with permittivity ∈ = 4.0. Then ______.

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


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