The electric field of an electromagnetic wave in free space is given by –
, where t and x are in seconds and metres respectively. It can be inferred that:
(a) The wavelength λ is 188.4 m
(b) The wave number k is 0.33 rad / m
(c) The wave amplitude is 10 V / m
(d) The wave is propagating along + x direction
Which one of the following pairs of statements is correct?
1. (a) and (b)
2. (b) and (c)
3. (c) and (d)
4. (a) and (c)
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. |
1. | \( b>a>c \) | 2. | \( a>b>c \) |
3. | \( c>b>a \) | 4. | \( a>c>b\) |
If \(\lambda_{v}, \lambda_{x},\) and \(\lambda_{m}\) represent the wavelengths of visible light, \(x\text-\)rays and microwaves respectively, then:
1. \( \lambda_{m}>\lambda_{x}>\lambda_{v} \)
2. \( \lambda_{v}>\lambda_{m}>\lambda_{x } \)
3. \( \lambda_{v}>\lambda_{x}>\lambda_{m }\)
4. \(\lambda_{m}>\lambda_{v}>\lambda_{x}\)
Which of the following has the minimum wavelength?
1. \(X\text-\)rays
2. Ultraviolet rays
3. \(\gamma\text-\)rays
4. Cosmic rays
What is the cause of “Greenhouse effect”?
1. Infra-red rays
2. Ultraviolet rays
3. \(X\text-\)rays
4. Radio waves
If the frequency of an EM wave is \(10\) MHz, then its wavelength is:
1. \(30\) m
2. \(300\) m
3. \(3\) m
4. none of the above
The velocity of electromagnetic waves is parallel to:
1.
2.
3.
4.
The biological importance of the ozone layer is:
1. | it stops ultraviolet rays. |
2. | ozone layer reduces the greenhouse effect. |
3. | ozone layer reflects radio waves. |
4. | ozone layer controls \(\mathrm{O}_2 / \mathrm{H}_2\) ratio in the atmosphere. |
The magnetic field in a plane electromagnetic wave is given by:
\(B_y = 2\times10^{-7} ~\text{sin}\left(\pi \times10^{3}x+3\pi\times10^{11}t\right )\text{T}\)
The wavelength is:
1. \(\pi\times 10^{3}~\text{m}\)
2. \(2\times10^{-3}~\text{m}\)
3. \(2\times10^{3}~\text{m}\)
4. \(\pi\times 10^{-3}~\text{m}\)