The Speed of EM Waves

Q.

The distance between two consecutive crests in a wave train produced in a

string is 5 cm. If 2 complete waves pass through any point per second, the

velocity of the wave is [CPMT 1990]

1. 10 cm/sec

2. 2.5 cm/sec

3. 5 cm/sec

4. 15 cm/sec

Q. Which of the given relations is correct?
$(c$ is speed of light, $E$ is electric field strength and $B$ is magnetic field strength$)$

1. $C=\frac{1}{{\mu }_0{\epsilon }_0}$
2. $EB=C$
3. $E=BC$
4. $EC=B$

Q. Speed of electromagnetic waves is the same

1. For all wavelengths
2. In all media
3. For all intensities
4. For all frequencies

Q.

Light is an electromagnetic wave. Its speed in vacuum is given by the expression

1. $\sqrt{{\mu }_0{e}_0}$

2. $\sqrt{\frac{{\mu }_0}{e_0}}$

3. $\sqrt{\frac{e_0}{{\mu }_0}}$

4. $\frac{1}{\sqrt{{\mu }_0{e}_0}}$

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. 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. Given magnetic field in a plane electromagnetic wave is given by $\overrightarrow{B}=3\times {10}^{-8}\sin (\omega t-kx+\varphi )\hat{j}$, then what will be expression for the electric field $\left(\overrightarrow{E}\right)$?

1. $\overrightarrow{E}=3\times {10}^{-8}\sin (1.6\times {10}^{3}x+48\times {10}^{10}t)\hat{i}\text{V/m}$
2. $\overrightarrow{E}=3\times {10}^{-8}\sin (1.6\times {10}^{3}x+48\times {10}^{10}t)\hat{j}\text{V/m}$
3. $\overrightarrow{E}=60\sin (1.6\times {10}^{3}x+48\times {10}^{10}t)\hat{k}\text{V/m}$
4. $\overrightarrow{E}=9\sin (1.6\times {10}^{3}x+48\times {10}^{10}t)\hat{k}\text{V/m}$