Q. No.| Assertion (A): | Light can travel in vacuum where as sound cannot do so. |
| Reason (R): | Light is an electromagnetic wave whereas sound is a mechanical wave. |
| 1. | Both (A) and (R) are True and (R) is the correct explanation of (A). |
| 2. | Both (A) and (R) are True but (R) is not the correct explanation of (A). |
| 3. | (A) is True but (R) is False. |
| 4. | Both (A) and (R) are False. |
An EM wave radiates outwards from a dipole antenna, with \(E_0\), as the amplitude of its electric field vector. The electric field \(E_0\), which transports significant energy from the source falls off as:
1. \(\dfrac{1}{r^3}\)
2. \(\dfrac{1}{r^2}\)
3. \(\dfrac{1}{r}\)
4. remains constant
1. \(E_0 \hat i\)
2. \(\dfrac {E_0} { \sqrt 2}\) \(\hat i \)
3. \(\sqrt 2E_0 \hat i\)
4. zero
A charged particle oscillates about its mean equilibrium position with a frequency of \(10^9 \text{ Hz}\). The electromagnetic waves produced:
| (a) | will have frequency of \(2×10^9 \text{ Hz}\) |
| (b) | will have frequency of \(10^9 \text{ Hz}\) |
| (c) | will have wavelength of \(0.3\) m |
| (d) | fall in the region of radiowaves |
Choose the correct options:
| 1. | (a), (b), (c) | 2. | (a), (c), (d) |
| 3. | (b), (c), (d) | 4. | (c), (d) |
| 1. | \( 2.16~\text{cm}, 24.1~\text{GHz} \) | 2. | \( 0.29~\text{cm}, 13.7~\text{GHz} \) |
| 3. | \( 3.23 ~\text{cm}, 20.0~\text{GHz} \) | 4. | \( 1.26~\text{cm}, 23.9~\text{GHz}\) |
| 1. | in the \({x\text{-}y}\) plane and they are parallel to each other. |
| 2. | in the \({x\text{-}y}\) plane and they are mutually perpendicular to each other. |
| 3. | in the \({y\text{-}z}\) plane and they are mutually perpendicular to each other. |
| 4. | in the \({z\text{-}x}\) plane and they are parallel to each other. |
The maximum value of the electric field in the wave is:
1. \(\dfrac {E_0} {\sqrt 2}\)
2. \(E_0\)
3. \(\sqrt 2 E_0\)
4. \(\sqrt 3 E_0\)
The amplitude of the magnetic field part of a harmonic electromagnetic wave in a vacuum is \(B_0=510~\text{nT}\). What is the amplitude of the electric field part of the wave?
1. \(200~\text{N/C}\)
2. \(153~\text{N/C}\)
3. \(150~\text{N/C}\)
4. \(510~\text{N/C}\)
1. \(\hat{j}+\hat{k},~-\hat{j}-\hat{k}\)
2. \(-\hat{j}+\hat{k},~-\hat{j}+\hat{k}\)
3. \(\hat{j}+\hat{k},~\hat{j}+\hat{k}\)
4. \(-\hat{j}+\hat{k},~-\hat{j}-\hat{k}\)
The magnetic field in a plane electromagnetic wave is given by:
\(B_y = 2\times10^{-7} ~\text{sin}\left(\pi \times10^{3}x+3\pi\times10^{11}t\right )\text{T}\)
The wavelength is:
1. \(\pi\times 10^{3}~\text{m}\)
2. \(2\times10^{-3}~\text{m}\)
3. \(2\times10^{3}~\text{m}\)
4. \(\pi\times 10^{-3}~\text{m}\)
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