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Electromagnetic Waves — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsElectromagnetic Waves1 Mark
MCQ
Consider an electromagnetic wave propagating in vacuum. Choose the correct statement:
  • A
    For an electromagnetic wave propagating in $+y$ direction the $1$ A electric field is $\overrightarrow{\text{E}}=\frac{1}{\sqrt{2}}\text{E}_\text{yz}(\text{x,t})\hat{\text{z}}$ and the magnetic field is $\overrightarrow{\text{B}}=\frac{1}{\sqrt{2}}\text{B}_\text{z}(\text{x,t})\hat{\text{y}}$
  • B
    For an electromagnetic wave propagating in $+y$ direction the electric field is $\overrightarrow{\text{E}}=\frac{1}{\sqrt{2}}\text{E}_\text{yz}(\text{x,t})\hat{\text{y}}$ and the magnetic field is $\overrightarrow{\text{B}}=\frac{1}{\sqrt{2}}\text{B}_\text{z}(\text{x,t})\hat{\text{z}}$
  • C
    For an electromagnetic wave propagating in $+x $ direction the electric field is $\overrightarrow{\text{E}}=\frac{1}{\sqrt{2}}\text{E}_\text{yz}(\text{y,z,t})(\hat{\text{y}}+\hat{\text{z}})$ and the magnetic field is $\overrightarrow{\text{B}}=\frac{1}{\sqrt{2}}\text{E}_\text{yz}(\text{x,t})(\hat{\text{y}}+\hat{\text{z}})$
  • ✓
    For an electromagnetic wave propagating in $+x$ direction the electric field is $\overrightarrow{\text{E}}=\frac{1}{\sqrt{2}}\text{E}_\text{yz}(\text{x,t})(\hat{\text{y}}-\hat{\text{z}})$ and the magnetic field is $\overrightarrow{\text{B}}=\frac{1}{\sqrt{2}}\text{E}_\text{yz}(\text{x,t})(\hat{\text{y}}+\hat{\text{z}})$
✓

Answer

Correct option: D.
For an electromagnetic wave propagating in $+x$ direction the electric field is $\overrightarrow{\text{E}}=\frac{1}{\sqrt{2}}\text{E}_\text{yz}(\text{x,t})(\hat{\text{y}}-\hat{\text{z}})$ and the magnetic field is $\overrightarrow{\text{B}}=\frac{1}{\sqrt{2}}\text{E}_\text{yz}(\text{x,t})(\hat{\text{y}}+\hat{\text{z}})$

Electromagnetic waves travel in the direction perpendicular to electric as well as magnetic field. Cross product of electric and magnetic field should give the direction of electromagnetic wave.

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