If \(\lambda_{\mathrm{v}}, \lambda_{\mathrm{x}},\) and\(\lambda_\mathrm{m}\) represent the wavelengths of visible light, x-rays and microwaves respectively, then:
1. \( \lambda_{\mathrm{m}}>\lambda_{\mathrm{x}}>\lambda_{\mathrm{v}} \)
2. \( \lambda_\mathrm{v}>\lambda_\mathrm{m}>\lambda_\mathrm{x } \)
3. \( \lambda_\mathrm{v}>\lambda_\mathrm{x}>\lambda_\mathrm{m }\)
4. \(\lambda_{\mathrm{m}}>\lambda_{\mathrm{v}}>\lambda_{\mathrm{x}}\)
Which of the following has the minimum wavelength?
1. X-rays
2. Ultraviolet rays
3. γ-rays
4. Cosmic rays
What is the cause of “Greenhouse effect”?
1. Infra-red rays
2. Ultraviolet rays
3. X-rays
4. Radio waves
The frequency order for \(\gamma\) - rays (\(b\)), X – rays (\(a\)), and UV – rays (\(c\)) is:
1. | \( b>a>c \) | 2. | \( a>b>c \) |
3. | \( c>b>a \) | 4. | \( a>c>b\) |
The ratio of the amplitude of a magnetic field to the amplitude of an electric field for an electromagnetic wave propagating in a vacuum is equal to:
1. | reciprocal of speed of light in vacuum. |
2. | the ratio of magnetic permeability to the electric susceptibility of vacuum. |
3. | unity. |
4. | the speed of light in a vacuum. |
The magnetic field in a plane electromagnetic wave is given by:
\(B_y = 2\times10^{-7} \text{sin}\left(\pi \times10^{3}x+3\pi\times10^{11}t\right )T\)
The wavelength is:
1. \(\pi\times 10^{3}~\text{m}\)
2. \(2\times10^{-3}~\text{m}\)
3. \(2\times10^{3}~\text{m}\)
4. \(\pi\times 10^{-3}~\text{m}\)
The EM wave with the shortest wavelength among the following is:
1. | Ultraviolet rays | 2. | \(X\)-rays |
3. | Gamma-rays | 4. | Microwaves |
Which of the following is not an electromagnetic wave?
1. Radio wave
2. Micro wave
3. Cosmic rays
4. -rays
If an electromagnetic wave propagating through vacuum is described by \(E_y= E_0 sin(kx-\omega t); ~B_z= B_0sin(kx-\omega t),\)then:
1. \(E_0k=B_0\omega\)
2. \(E_0B_0 = \omega k\)
3. \(E_0\omega= B_0k\)
4. \(E_0B_0= \frac{\omega}{k}\)
The electric field part of an electromagnetic wave in vacuum is,
\(\vec{E}=(3.1 \mathrm{~N} / \mathrm{C}) \cos \left[(1.8~ \mathrm{rad} / \mathrm{m}) y+\left(5.4 \times 10^8 ~\mathrm{rad} / \mathrm{s}\right) \mathrm{t}\right] \hat{i}\).
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. \(7.5\times 10^{7}~\text{Hz}\)