Q. No.The ratio of contributions made by the electric field and magnetic field components to the intensity of an electromagnetic wave is: (\(c\) = speed of electromagnetic waves)
1.
\(1:1\)
2.
\(1:c\)
3.
\(1:c^2\)
4.
\(c:1\)
Light with an average flux of \(20~\text{W/cm}^2\) falls on a non-reflecting surface at normal incidence having a surface area \(20~\text{cm}^2\). The energy received by the surface during time span of \(1\) minute is:
1. \(12\times 10^{3}~\text{J}\)
2. \(24\times 10^{3}~\text{J}\)
3. \(48\times 10^{3}~\text{J}\)
4. \(10\times 10^{3}~\text{J}\)
A capacitor is made of two circular plates each of radius \(12~\text{cm}\) and separated by \(5.0~\text{cm}\). The capacitor is being charged by an external source. The charging current is constant and equal to \(0.15~\text{A}\). The displacement current across the plates is:
1. \(0\)
2. \(0.14~\text{A}\)
3. \(0.16~\text{A}\)
4. \(0.15~\text{A}\)
A parallel plate capacitor made of circular plates each of radius \(R=6.0\) cm has a capacitance \(C=100\) pF. The capacitor is connected to a \(230\) V AC supply with an (angular) frequency of \(300\) rad/s. The amplitude of \(\vec{B}\) at the point \(3\) cm from the axis between the plate is:
1. \(1.12\times 10^{-11}\) T
2. \(2.01\times 10^{-12}\) T
3. \(1.63\times 10^{-11}\) T
4. \(1.01\times 10^{-12}\) T
A plane electromagnetic wave travels in a vacuum along the \({z\text{-}}\)direction. Then the directions of its electric and magnetic field vectors will be:
| 1. | in the \({x\text{-}y}\) plane and they are parallel to each other. |
| 2. | in the \({x\text{-}y}\) plane and they are mutually perpendicular to each other. |
| 3. | in the \({y\text{-}z}\) plane and they are mutually perpendicular to each other. |
| 4. | in the \({z\text{-}x}\) plane and they are parallel to each other. |
A radio can tune in to any station in the \(7.5\) MHz to \(12\) MHz bands. What is the corresponding wavelength band?
1. \(40\) to \(25\) m
2. \(10\) to \(100\) m
3. \(50\) to \(60\) m
4. \(20\) to \(10\) m
1. \(10^{11}\) Hz
2. \(10^7\) Hz
3. \(10^8\) Hz
4. \(10^9\) Hz
Which physical quantity does not change in vacuum for X-rays?
| 1. | speed of light | 2. | wavelength |
| 3. | frequency | 4. | none of these |
The amplitude of the magnetic field part of a harmonic electromagnetic wave in a vacuum is \(B_0=510~\text{nT}\). What is the amplitude of the electric field part of the wave?
1. \(200~\text{N/C}\)
2. \(153~\text{N/C}\)
3. \(150~\text{N/C}\)
4. \(510~\text{N/C}\)
Suppose that the electric field amplitude of an electromagnetic wave is \(E_0 = 120~\text{N/C}\) and that its frequency is \(\nu = 50.0~\text{MHz}\). The value of \(k\) is:
1. \(2.01~\text{rad/m}\)
2. \(1.72~\text{rad/m}\)
3. \(1.05~\text{rad/m}\)
4. \(2.41~\text{rad/m}\)
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