The Speed of EM Waves

Q. Dimentional formula of permeability of free space ${\mu }_0$ is given by

1. $\left[M^{0}L{T}^{-2}{A}^{-2}\right]$
2. $\left[M{L}^2{T}^{-1}{A}^{-2}\right]$
3. $\left[ML{T}^{-2}{A}^{-2}\right]$
4. $\left[M^{0}L{T}^{-1}{A}^{-1}\right]$

Q.

The refractive index and the permeability of a medium are $1.5H{m}^{-1}$ and $5\times {10}^{-7}H{m}^{-1}$ respectively. The relative permittivity of the medium is nearly

1. $25$

2. $15$

3. $81$

4. $10$

5. $6$

Q. An $LC$ circuit contains inductance $L=1\mu \text{H}$ and capacitance $C=0.01\mu \text{F}$. The wavelength of electromagnetic wave generated is nearly

1. $0.5\text{m}$
2. $5\text{m}$
3. $190\text{m}$
4. $30\text{m}$

Q.

In a wave $E_0=100V{m}^{-1}$. Find the Poynting vector magnitude.

1. $13.25W{m}^{-2}$

2. $26.5W{m}^{-2}$

3. $18.25W{m}^{-2}$

4. $19.7W{m}^{-2}$

Q. How does the speed of electromagnetic wave in vacuum depend upon the source of radiation?

1. Increases as we move from g-rays to radio waves
2. Decreases as we move from g-rays to radio waves
3. Is same for all of them
4. None of these

Q. If ${ϵ}_0$ and ${\mu }_0$ represent the permittivity and permeability of vacuum and $ϵ$ and $\mu$ represent the permittivity and permeability of medium, then refractive index of the medium is given by

1. $\sqrt{\frac{\mu ϵ}{{\mu }_0{ϵ}_0}\mu ϵ}$
2. $\sqrt{\frac{\mu ϵ}{{\mu }_0{ϵ}_0}}$
3. $\sqrt{\frac{\mu }{{\mu }_0{ϵ}_0}}$
4. $\sqrt{\frac{{\mu }_0{ϵ}_0}{\mu }}$

Q. If ${ϵ}_0$ and ${\mu }_0$ represent the permittivity and permeability of vacuum and $ϵ$ and $\mu$ represent the permittivity and permeability of medium, then refractive index of the medium is given by

1. $\sqrt{\frac{\mu ϵ}{{\mu }_0{ϵ}_0}\mu ϵ}$
2. $\sqrt{\frac{\mu ϵ}{{\mu }_0{ϵ}_0}}$
3. $\sqrt{\frac{\mu }{{\mu }_0{ϵ}_0}}$
4. $\sqrt{\frac{{\mu }_0{ϵ}_0}{\mu }}$

Q. In an electromagnetic wave in free space, the root mean square value of the electric field is $E_{rms}=6V/m$. The peak value of the magnetic field is

1. $4.23\times {10}^{-8}T$
2. $1.41\times {10}^{-8}T$
3. $2.83\times {10}^{-8}T$
4. $0.70\times {10}^{-8}T$

Q. Which of the following have zero average value in a plane electromagnetic wave?

1. Electric field
2. Magnetic field
3. Electric energy
4. Magnetic energy