Q. No.An EM wave is propagating in a medium with a velocity \(\overrightarrow{{v}}={v} \hat{i}\). The instantaneous oscillating electric field of this EM wave is along the \(+y\) axis. The direction of the oscillating magnetic field of the EM wave will be along:
1. \(-z \text-\)direction
2. \(+z \text-\) direction
3. \(-y \text-\) direction
4. \(+y \text-\) direction
1. \(-z \text-\)direction
2. \(+z \text-\) direction
3. \(-y \text-\) direction
4. \(+y \text-\) direction
A \(100~\Omega\) resistance and a capacitor of \(100~\Omega\) reactance are connected in series across a \(220~\text{V}\) source. When the capacitor is \(50\%\) charged, the peak value of the displacement current is:
1. \(2.2~\text{A}\)
2. \(11~\text{A}\)
3. \(4.4~\text{A}\)
4. \(11\sqrt{2}~\text{A}\)
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. \(1.41\times 10^{-8}~\text{T}\)
Out of the following options which one can be used to produce a propagating electromagnetic wave?
| 1. | a stationary charge. |
| 2. | a chargeless particle. |
| 3. | an accelerating charge. |
| 4. | a charge moving at constant velocity. |
The energy of the EM waves is of the order of \(15~\mathrm{keV}\). To which part of the spectrum does it belong?
1. X-rays
2. Infrared rays
3. Ultraviolet rays
4. \(\gamma\)-rays
Light with an energy flux of \(25\times10^4\) Wm–2 falls on a perfectly reflecting surface at normal incidence. If the surface area is \(15\) cm2, the average force exerted on the surface is:
1. \(1.25\times 10^{-6}\) N
2. \(2.50\times 10^{-6}\) N
3. \(1.20\times 10^{-6}\) N
4. \(3.0\times 10^{-6}\) N
The condition under which a microwave oven heats up a food item containing water molecules most efficiently is:
| 1. | the frequency of microwaves has no relation with the natural frequency of water molecules. |
| 2. | microwaves are heatwaves, so always produce heating. |
| 3. | infrared waves produce heating in a microwave oven. |
| 4. | the frequency of the microwaves must match the resonant frequency of the water molecules. |
1. \(2~\mathrm{m}^{-1}\)
2. \(0.5~\mathrm{m}^{-1}\)
3. \(6~\mathrm{m}^{-1}\)
4. \(3~\mathrm{m}^{-1}\)
The electric and the magnetic fields, associated with an electromagnetic wave, propagating along the positive Z-axis, can be represented by:
1. \(\left [E=E_{0}\hat{k},~B=B_{0}\hat{i} \right ]\)
2. \(\left [E=E_{0}\hat{j},~B=B_{0}\hat{j} \right ]\)
3. \(\left [E=E_{0}\hat{j},~B=B_{0}\hat{k} \right ]\)
4. \(\left [E=E_{0}\hat{i},~B=B_{0}\hat{j} \right ]\)
| 1. | gamma rays, ultraviolet, infrared, microwaves. |
| 2. | microwaves, gamma rays, infrared, ultraviolet. |
| 3. | infrared, microwave, ultraviolet, gamma rays. |
| 4. | microwave, infrared, ultraviolet, gamma rays. |
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