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 \(Y\) |
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
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. |
1. | \(1:1\) | 2. | \(1:c\) |
3. | \(1:c^2\) | 4. | \(c:1\) |
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
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
In an electromagnetic wave, if the electric field oscillated sinusoidally with an amplitude of \(48~\text{Vm}^{-1}\), then the RMS value of the oscillating magnetic field will be:
1. \(1.6\times 10^{-8}~\text{T}\)
2. \(1.6\times 10^{-9}~\text{T}\)
3. \(144\times 10^{-8}~\text{T}\)
4. \(11.3\times 10^{-8}~\text{T}\)
The sun delivers \(10^{3}~\text{W/m}^2\) of electromagnetic flux to the earth's surface. The total power that is incident on a roof of dimensions \(8\) m\(20\) m will be:
1. \(2.56\times 10^{4}~\text{W}\)
2. \(6.4\times 10^{5}~\text{W}\)
3. \(4.0\times 10^{5}~\text{W}\)
4. \(1.6\times 10^{5}~\text{W}\)