Q. No.In an electromagnetic wave in free space, the root mean square value of the electric field is \(E_{\text{rms}} = 6~\text{V/m}\). The peak value of the magnetic field is:
1. \(2.83\times 10^{-8}~\text{T}\)
2. \(0.70\times 10^{-8}~\text{T}\)
3. \(4.23\times 10^{-8}~\text{T}\)
4. \(1.41\times 10^{-8}~\text{T}\)
1. \(\gamma , \alpha, \beta \)
2. \( \alpha, \beta , \gamma \)
3. \( \beta, \alpha , \gamma \)
4. \(\beta, \gamma, \alpha \)
| 1. | wavelength is doubled and frequency becomes half |
| 2. | wavelength is halved and frequency remains unchanged |
| 3. | wavelength and frequency both remain unchanged |
| 4. | wavelength is doubled and frequency unchanged |
| 1. | wavelength is \(2\) times and frequency becomes half. |
| 2. | wavelength is half and frequency remains unchanged. |
| 3. | wavelength and frequency both remain unchanged. |
| 4. | None of the above. |
The electric field associated with an electromagnetic wave in vacuum is given by \(E=40 \cos \left(k z-6 \times 10^8 t\right)\), where \(E\), \(z\), and \(t\) are in volt/m, meter, and second respectively.
The value of the wave vector \(k\) would be:
1. \(2~\text{m}^{-1}\)
2. \(0.5~\text{m}^{-1}\)
3. \(6~\text{m}^{-1}\)
4. \(3~\text{m}^{-1}\)
Light with an average flux of \(20~\text{W/cm}^2\) falls on a non-reflecting surface at normal incidence having a surface area \(20~\text{cm}^2\). The energy received by the surface during time span of \(1\) minute is:
1. \(12\times 10^{3}~\text{J}\)
2. \(24\times 10^{3}~\text{J}\)
3. \(48\times 10^{3}~\text{J}\)
4. \(10\times 10^{3}~\text{J}\)
| 1. | the energy density in electric field is equal to energy density in magnetic field. |
| 2. | they travel with a speed equal to \(\dfrac{1}{\sqrt{\mu_0~ \varepsilon_0}} .\) |
| 3. | they originate from charges moving with uniform speed. |
| 4. | they are transverse in nature. |
1. \(2~\text{m}^{-1}\)
2. \(0.5~\text{m}^{-1}\)
3. \(6~\text{m}^{-1}\)
4. \(3~\text{m}^{-1}\)
The ratio of the amplitude of a magnetic field to the amplitude of an electric field for an electromagnetic wave propagating in a vacuum is equal to:
| 1. | reciprocal of speed of light in vacuum. |
| 2. | the ratio of magnetic permeability to the electric susceptibility of vacuum. |
| 3. | unity. |
| 4. | the speed of light in a vacuum. |
1. \(\sqrt2\)
2. \(\sqrt3\)
3. \(3\)
4. \(2\)
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