An electromagnetic wave is moving along negative \(\text{z (-z)}\) direction and at any instant of time, at a point, its electric field vector is \(3\hat j~\text{V/m}\). The corresponding magnetic field at that point and instant will be: (Take \(c=3\times10^{8}~\text{ms}^{-1}\) )
1. | \(10\hat i~\text{nT}\) | 2. | \(-10\hat i~\text{nT}\) |
3. | \(\hat i~\text{nT}\) | 4. | \(-\hat i~\text{nT}\) |
1. | \(3 \times 10^{-8} \text{cos}\left(1.6 \times 10^3 x+48 \times 10^{10} t\right) \hat{i}~\text{ V/m}\) |
2. | \(3 \times 10^{-8} \text{sin} \left(1.6 \times 10^3 {x}+48 \times 10^{10} {t}\right) \hat{{i}}~ \text{V} / \text{m}\) |
3. | \(9 \text{sin} \left(1.6 \times 10^3 {x}-48 \times 10^{10} {t}\right) \hat{{k}} ~~\text{V} / \text{m}\) |
4. | \(9 \text{cos} \left(1.6 \times 10^3 {x}+48 \times 10^{10} {t}\right) \hat{{k}}~~\text{V} / \text{m}\) |
The ratio of contributions made by the electric field and magnetic field components to the intensity of an electromagnetic wave is: (\(c\) = speed of electromagnetic waves)
1. | \(1:1\) | 2. | \(1:c\) |
3. | \(1:c^2\) | 4. | \(c:1\) |
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. \(10\times 10^{3}~\text{J}\)
The magnetic field in a plane electromagnetic wave is given by:
\(B_y = 2\times10^{-7} \text{sin}\left(\pi \times10^{3}x+3\pi\times10^{11}t\right )T\)
The wavelength is:
1. \(\pi\times 10^{3}~\text{m}\)
2. \(2\times10^{-3}~\text{m}\)
3. \(2\times10^{3}~\text{m}\)
4. \(\pi\times 10^{-3}~\text{m}\)