An electromagnetic wave is moving along negative \(z (-z)\) 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.
\(-\hat i~\text{nT}\)
In a photoelectric experiment, blue light is capable of ejecting a photoelectron from a specific metal while green light is not able to eject a photoelectron. Ejection of photoelectrons is also possible using light of the colour:
1. yellow
2. red
3. violet
4. orange
1. \(0.9~\mu\text{F}\)
2. \(0.09~\mu\text{F}\)
3. \(0.1~\mu\text{F}\)
4. \(0.01~\mu\text{F}\)
A string of length \(l\) is fixed at both ends and is vibrating in second harmonic. The amplitude at antinode is \(2\) mm. The amplitude of a particle at a distance \(l/8\) from the fixed end is:
1. \(2\sqrt2~\text{mm}\)
2. \(4~\text{mm}\)
3. \(\sqrt2~\text{mm}\)
4. \(2\sqrt3~\text{mm}\)
The circuit represents a full wave bridge rectifier when switch \(S\) is open. The output voltage \((\text V_0)\) pattern across \(R_L\) when \(S\) is closed:
| 1. |  |
2. |  |
| 3. |  |
4. |  |
| Assertion (A): | Gauss's law for magnetism states that the net magnetic flux through any closed surface is zero. |
| Reason (R): | The magnetic monopoles do not exist. North and South poles occur in pairs, allowing vanishing net magnetic flux through the surface. |
| 1. | (A) is True but (R) is False. |
| 2. | (A) is False but (R) is True. |
| 3. | Both (A) and (R) are True and (R) is the correct explanation of (A). |
| 4. | Both (A) and (R) are True but (R) is not the correct explanation of (A). |
An AC source given by \(V=V_m\sin\omega t\) is connected to a pure inductor \(L\) in a circuit and \(I_m\) is the peak value of the AC current. The instantaneous power supplied to the inductor is:
1. \(\dfrac{V_mI_m}{2}\mathrm{sin}(2\omega t)\)
2. \(-\dfrac{V_mI_m}{2}\mathrm{sin}(2\omega t)\)
3. \({V_mI_m}\mathrm{sin}^{2}(\omega t)\)
4. \(-{V_mI_m}\mathrm{sin}^{2}(\omega t)\)
The fraction of the original number of radioactive atoms that disintegrates (decays) during the average lifetime of a radioactive substance will be:
1. \(\frac{1}{e}\)
2. \(\frac{1}{1+e}\)
3. \(\frac{e-1}{e+1}\)
4. \(\frac{e-1}{e}\)
The figure given below shows the displacement and time, \((x\text -t)\) graph of a particle moving along a straight line:
The correct statement, about the motion of the particle, is:
| 1. | the particle moves at a constant velocity up to a time \(t_0\) and then stops. |
| 2. | the particle is accelerated throughout its motion. |
| 3. | the particle is accelerated continuously for time \(t_0\) then moves with constant velocity. |
| 4. | the particle is at rest. |
Air is pushed carefully into a soap bubble of radius \(r\) to double its radius. If the surface tension of the soap solution is \(T,\) then work done in the process is:
| 1. | \(12\pi r^2T\) | 2. | \(24\pi r^2T\) |
| 3. | \(4\pi r^2T\) | 4. | \(8\pi r^2T\) |
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