Which colour of light has the longest wavelength?

1. violet

2. red

3. blue

4. green

Choose the correct option:

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?

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

The figure shows a parallel plate capacitor being charged by a battery. If \(X\) and \(Y\) are two closed curves then during charging, \(\oint \vec{B}.d\vec{l}\) is zero along the curve:

        
1. \(X\) only
2. \(Y\) only
3.  Both \(X\) & \(Y\)
4.  Neither \(X\) nor \(Y\)

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. $\mathrm{\gamma }$-rays

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

A larger parallel plate capacitor, whose plates have an area of \(1~\text{m}^2,\) separated from each other by \(1~\text{mm},\) is being charged at a rate of \(25.8~\text{V/s}.\) If the plates have a 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. \(1.1~\mu\text{A}\)