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Question

The amplitude of the magnetic field part of a harmonic electromagnetic wave in vaccum is B 0 = 480 nT. Find the amplitude of the electric field part of the wave?

The correct answer is 144 N/C

Electromagnetic Wave Fields in Vacuum

An electromagnetic (EM) wave consists of oscillating electric and magnetic fields that are perpendicular to each other and also perpendicular to the direction of wave propagation. In a vacuum, these waves travel at a constant speed, which is the speed of light.

Magnetic Field Amplitude Given

The problem provides the amplitude of the magnetic field part of a harmonic electromagnetic wave in vacuum. This value is given as:

  • Amplitude of magnetic field, \(B_0 = 480 \text{ nT}\)

To perform calculations, it is essential to convert the magnetic field amplitude from nanoTesla (nT) to Tesla (T). We know that \(1 \text{ nT} = 10^{-9} \text{ T}\).

Therefore, \(B_0 = 480 \times 10^{-9} \text{ T}\).

Electric Field Amplitude Calculation

In a vacuum, the amplitudes of the electric field (\(E_0\)) and the magnetic field (\(B_0\)) of an electromagnetic wave are directly related by the speed of light (\(c\)). The fundamental relationship is given by the formula:

\[E_0 = c \times B_0\]

Where:

  • \(E_0\) is the amplitude of the electric field in Newtons per Coulomb (N/C) or Volts per meter (V/m).
  • \(c\) is the speed of light in vacuum, which is approximately \(3 \times 10^8 \text{ m/s}\).
  • \(B_0\) is the amplitude of the magnetic field in Tesla (T).

Now, let's substitute the given value of \(B_0\) and the speed of light \(c\) into the formula to find the amplitude of the electric field:

\[E_0 = (3 \times 10^8 \text{ m/s}) \times (480 \times 10^{-9} \text{ T})\]

Performing the multiplication:

\[E_0 = (3 \times 480) \times (10^8 \times 10^{-9}) \text{ N/C}\]

\[E_0 = 1440 \times 10^{(8 - 9)} \text{ N/C}\]

\[E_0 = 1440 \times 10^{-1} \text{ N/C}\]

\[E_0 = 144 \text{ N/C}\]

Summary of Calculation

Parameter Value Unit
Magnetic Field Amplitude (\(B_0\)) \(480\) nT
Magnetic Field Amplitude (\(B_0\)) (converted) \(480 \times 10^{-9}\) T
Speed of Light (\(c\)) \(3 \times 10^8\) m/s
Electric Field Amplitude (\(E_0\)) \(144\) N/C

The calculated amplitude of the electric field part of the wave is \(144 \text{ N/C}\).

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Important Questions from Electromagnetic Waves

  1. Consider the two statements given below :

    Statement-1: Infrared waves are also called heat waves.

    Statement-2: Water molecules readily absorb infrared waves.

    Select the correct answer using the code given below:

  2. Consider the following statements about visible light, UV light and X-rays:

    1. The wavelength of visible light is more than that of X-rays.

    2. The energy of X-ray photons is higher than that of UV light photons.

    3. The energy of UV light photons is less than that of visible light photons.

    Which of the statements given above is/are correct?
  3. The wavelength of X-rays is of the order of

  4. Which of the followings are the characteristics of electromagnetic waves?

    1) They are elastic waves.

    2) They can also move in a vacuum.

    3) They have electric and magnetic components that are mutually perpendicular.

    4) They move with a speed equal to 3 lakh meters per second.

    Select the correct answer using the code given below:

  5. Which of the following devices is based on the phenomenon of electromagnetic induction?

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