Tamil Nadu Board of Secondary EducationHSC Science Class 12

Why are e.m. waves non-mechanical? - Physics

Advertisements
Advertisements
Short Note

Why are e.m. waves non-mechanical?

Advertisements

Solution

Electromagnetic waves are produced by an accelerated charge and do not require any medium for propagation. So electromagnetic wave is a non-mechanical wave.

  Is there an error in this question or solution?
Chapter 5: Electromagnetic waves - Evaluation [Page 283]

APPEARS IN

Tamil Nadu Board Samacheer Kalvi Class 12th Physics Volume 1 and 2 Answers Guide
Chapter 5 Electromagnetic waves
Evaluation | Q II. 8. | Page 283

RELATED QUESTIONS

Write any two important properties of electromagnetic waves.


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


When Sunita, a class XII student, came to know that her parents are planning to rent out the top floor of their house to a mobile company she protested. She tried hard to convince her parents that this move would be a health hazard.
Ultimately her parents agreed :

(1) In what way can the setting up of transmission tower by a mobile company in a residential colony prove to be injurious to health?

(2) By objecting to this move of her parents, what value did Sunita display?

(3) Estimate the range of e.m. waves which can be transmitted by an antenna of height 20 m. (Given radius of the earth = 6400 km)


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


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?


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.


Arrange the following electromagnetic waves in decreasing order of wavelength:

γ-rays, infrared rays, X-rays and microwaves.

Explain briefly how electromagnetic waves are produced by an oscillating charge. How is the frequency of the em waves produced related to that of the oscillating charge?


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


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


Can an electromagnetic wave be polarised?


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?


Displacement current goes through the gap between the plates of a capacitor when the charge of the capacitor

(a) increases
(b) decreases
(c) does not change
(d) is zero


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 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.


Consider the situation of the previous problem. Define displacement resistance Rd = V/idof the space between the plates, where V is the potential difference between the plates and id is the displacement current. Show that Rd varies with time as `R_d = R(e^(t"/"tau) - 1)` .


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 ______.


In an electromagnetic wave in free space the rms value of the electric field is 3 V m-1. The peak value of the magnetic field is ______.


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:


If the magnetic monopole exists, then which of the Maxwell’s equation to be modified?


Write notes on Gauss' law in magnetism.


What are Fraunhofer lines? How are they useful in the identification of elements present in the Sun?


Write a short note on the radio waves.


Discuss the Hertz experiment.


Write down the properties 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.


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 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 light in vacuum can be changed by changing


The velocity of electromagnetic wave is parallel to


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


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?


If `vecE` and `vecB` represent electric and magnetic field vectors of the electromagnetic wave, the direction of propagation of the electromagnetic wave is along ______.


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 ______.


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.


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


What is the source of energy of electromagnetic waves?


The diagram below shows the electric field (E) and magnetic field (B) components of an electromagnetic wave at a certain time and location.

The direction of the propagation of the electromagnetic wave is ______.


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


Share
Notifications



      Forgot password?
Use app×