NEET-XII-Physics
08: Electromagnetic Waves
- #11Suppose that the electric field part of an electromagnetic wave in vacuum is E = {(3.1 N/C) cos [(1.8 rad/m) y + (5.4 × 106 rad/s)t]}
.
(a) What is the direction of propagation?
(b) What is the wavelength λ?
(c) What is the frequency ν?
(d) What is the amplitude of the magnetic field part of the wave?
(e) Write an expression for the magnetic field part of the wave.
(a) What is the direction of propagation?
(b) What is the wavelength λ?
(c) What is the frequency ν?
(d) What is the amplitude of the magnetic field part of the wave?
(e) Write an expression for the magnetic field part of the wave.Ans : null (a) From the given electric field vector, it can be inferred that the electric field is directed along the negative x direction. Hence, the direction of motion is along the negative y direction i.e.,
.
(b) It is given that,
The general equation for the electric field vector in the positive x direction can be written as:
On comparing equations (1) and (2), we get
Electric field amplitude, E0 = 3.1 N/C
Angular frequency, ω = 5.4 × 108 rad/s
Wave number, k = 1.8 rad/m
Wavelength,
= 3.490 m
(c) Frequency of wave is given as:
(d) Magnetic field strength is given as:
Where,
c = Speed of light = 3 × 108 m/s
(e) On observing the given vector field, it can be observed that the magnetic field vector is directed along the negative z direction. Hence, the general equation for the magnetic field vector is written as:
(a) From the given electric field vector, it can be inferred that the electric field is directed along the negative x direction. Hence, the direction of motion is along the negative y direction i.e.,.
(b) It is given that,
The general equation for the electric field vector in the positive x direction can be written as:
On comparing equations (1) and (2), we get
Electric field amplitude, E0 = 3.1 N/C
Angular frequency, ω = 5.4 × 108 rad/s
Wave number, k = 1.8 rad/m
Wavelength, = 3.490 m
(c) Frequency of wave is given as:
(d) Magnetic field strength is given as:
Where,
c = Speed of light = 3 × 108 m/s
(e) On observing the given vector field, it can be observed that the magnetic field vector is directed along the negative z direction. Hence, the general equation for the magnetic field vector is written as:
- #11-aWhat is the direction of propagation?Ans : From the given electric field vector, it can be inferred that the electric field is directed along the negative x direction. Hence, the direction of motion is along the negative y direction i.e.,.
- #11-bWhat is the wavelength λ?Ans : It is given that,
The general equation for the electric field vector in the positive x direction can be written as:
On comparing equations (1) and (2), we get
Electric field amplitude, E0 = 3.1 N/C
Angular frequency, ω = 5.4 × 108 rad/s
Wave number, k = 1.8 rad/m
Wavelength, = 3.490 m
- #11-cWhat is the frequency ν?Ans : Frequency of wave is given as:
- #11-dWhat is the amplitude of the magnetic field part of the wave?Ans : Magnetic field strength is given as:
Where,
c = Speed of light = 3 × 108 m/s
- #11-eWrite an expression for the magnetic field part of the wave.Ans : On observing the given vector field, it can be observed that the magnetic field vector is directed along the negative z direction. Hence, the general equation for the magnetic field vector is written as: