|Class 12 Physics Electromagnetic Waves||Electromagnetic energy of each wave|
Electromagnetic energy of each wave in Electromagnetic Spectrum
Electromagnetic waves energy can be described by frequency, wavelength or energy.
Relation between Wavelength and Frequency
Problem:- 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?
Answer:- Amplitude of magnetic field of an electromagnetic wave in a vacuum,
B0 = 510 nT = 510 × 10−9 T
Speed of light in a vacuum, c = 3 × 108 m/s
Amplitude of electric field of the electromagnetic wave is given by the relation,
E = cB0 = 3 × 108 × 510 × 10−9 = 153 N/C
Therefore, the electric field part of the wave is 153 N/C.
Problem:- A plane electromagnetic wave travels in vacuum along z-direction.What can you say about the directions of its electric and magneticfield vectors? If the frequency of the wave is 30 MHz, what is itswavelength?
Answer:- The electromagnetic wave travels in a vacuum along the z-direction. The electric field (E) andthe magnetic field (H) are in the x-y plane. They are mutually perpendicular. Frequency ofthe wave, ν = 30 MHz = 30 × 106s−1
Speed of light in a vacuum, c = 3 × 108 m/s Wavelengthof a wave is given as:
λ =(c/ ν) = (3x108)/ (30x106)