The speed of an electromagnetic wave in a medium of dielectric constant \(2.25\) and relative permeability \(4\) is approximately:
1. \(1\times 10^{8}\) m/s
2. \(2.5\times 10^{8}\) m/s
3. \(3\times 10^{8}\) m/s
4. \(2\times 10^{8}\) m/s
The figure shows a parallel plate capacitor being charged by a battery. If \(X\) and \(Y\) are two closed curves then during charging, \(\oint \vec{B} . \vec{dl}\) is zero along the curve:
1. | \(X\) only |
2. | \(Y\) only |
3. | Both \(X\) & \(Y\) |
4. | Neither \(X\) nor \(Y\) |
A larger parallel plate capacitor, whose plates have an area of \(1~\text{m}^2,\) separated from each other by \(1\) mm, is being charged at a rate of \(25.8\) V/s.
If the plates have dielectric constant \(10\), then the displacement current at this instant is:
1. \(25~\mu\text{A}\)
2. \(11~\mu\text{A}\)
3. \(2.2~\mu\text{A}\)
4. \(1.1~\mu\text{A}\)
1. | wavelength is \(2\) times and frequency becomes half. |
2. | wavelength is half and frequency remains unchanged. |
3. | wavelength and frequency both remain unchanged. |
4. | None of the above. |
1. | Faraday's law of induction |
2. | Modified Ampere's law |
3. | Gauss's law of electricity |
4. | Gauss's law of magnetism |
The most penetrating radiation out of the following is:
1. \(X\text-\)rays
2. \(\beta\text-\)rays
3. \(\alpha\text-\)rays
4. \(\gamma\text-\)rays
Which of the following statements is false regarding the properties of electromagnetic waves?
1. | Both electric and magnetic field vectors attain the maxima and minima at the same place and the same time |
2. | The energy in an electromagnetic wave is divided equally between electric and magnetic vectors |
3. | Both electric and magnetic field vectors are parallel to each other and perpendicular to the direction of propagation of the wave |
4. | These waves do not require any material medium for propagation |
Which colour of light has the longest wavelength?
1. violet
2. red
3. blue
4. green
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. |
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