A capacitor is made of two circular plates each of radius \(12~\text{cm}\) and separated by \(5.0~\text{cm}\). The capacitor is being charged by an external source. The charging current is constant and equal to \(0.15~\text{A}\). The displacement current across the plates is:
1. \(0\)
2. \(0.14~\text{A}\)
3. \(0.16~\text{A}\)
4. \(0.15~\text{A}\)
The electric field part of an electromagnetic wave in vacuum is,
\(\vec{E}=(3.1~\text{N/C}) \cos \left[(1.8~\text{rad/m}) y+\left(5.4 \times 10^8 ~\text{rad/s}\right)t\right] \hat{i}.\)
What is the frequency of the wave?
1. \(5.7\times 10^{7}~\text{Hz}\)
2. \(9.3\times 10^{7}~\text{Hz}\)
3. \(8.6\times 10^{7}~\text{Hz}\)
4. \(7.5\times 10^{7}~\text{Hz}\)
If an electromagnetic wave propagating through vacuum is described by \(E_y= E_0 \sin(kx-\omega t); ~B_z= B_0\sin(kx-\omega t),\) then:
1. \(E_0k=B_0\omega\)
2. \(E_0B_0 = \omega k\)
3. \(E_0\omega= B_0k\)
4. \(E_0B_0= \frac{\omega}{k}\)
Which of the following is not an electromagnetic wave?
1. Radio wave
2. Micro wave
3. Cosmic rays
4. -rays
Consider an oscillator which has a charged particle oscillating about its mean position with a frequency of \(300\) MHz. The wavelength of electromagnetic waves produced by this oscillator would be:
1. \(1\) m
2. \(10\) m
3. \(100\) m
4. \(1000\) m
1. | \(1:1\) | 2. | \(1:c\) |
3. | \(1:c^2\) | 4. | \(c:1\) |
Which statement is correct for X-rays and gamma rays?
1. | X-rays are emitted from electronic transitions while gamma rays are emitted from nuclear transitions. |
2. | X-rays have less penetrating power in comparison to gamma rays, in general. |
3. | The frequency of gamma rays is more than the frequency of X-rays, in general. |
4. | All of the above. |
The magnetic field amplitude of an electromagnetic wave is \(2\times 10^{-7}~\text{T}\). Its electric field amplitude if the wave is travelling in free space is:
1. \(6~\text{Vm}^{-1}\)
2. \(60~\text{Vm}^{-1}\)
3. \(\frac{10}{6}~\text{Vm}^{-1}\)
4. None of these
Choose the correct option:
1. | The radiation in increasing order of frequency are radio waves, microwaves, infrared, visible, ultraviolet, X-rays, gamma rays. |
2. | The wavelength of colours in increasing order is violet, indigo, green, yellow, orange and red. |
3. | The speed of light is maximum in vacuum. |
4. | All options are correct. |