A lamp radiates power \(P_0\) uniformly in all directions. The amplitude of electric field strength \(E_0\) at a distance \(r\) from it is:
1. \(E_{0} = \frac{P_{0}}{2 \pi\varepsilon_{0} cr^{2}}\)
2. \(E_{0} = \sqrt{\frac{P_{0}}{2 \pi\varepsilon_{0} cr^{2}}}\)
3. \(E_{0} = \sqrt{\frac{P_{0}}{4 \pi\varepsilon_{0} cr^{2}}}\)
4. \(E_{0} = \sqrt{\frac{P_{0}}{8 \pi\varepsilon_{0} cr^{2}}}\)
The intensity of visible radiation at a distance of \(1\) m from a bulb of \(100\) W which converts only \(5\%\) of its power into light, is:
1. \(0.4\) W/m2
2. \(0.5\) W/m2
3. \(0.1\) W/m2
4. \(0.01\) W/m2
A. | \(X\text-\)rays in vacuum travel faster than light waves in vacuum. |
B. | The energy of an \(X\text-\)ray photon is greater than that of a light photon. |
C. | Light can be polarised but \(X\text-\)ray cannot. |
1. A and B
2. B and C
3. A, B and C
4. B only
1. | \(\oint_S \vec{E} \cdot \overrightarrow{d S}=\frac{1}{\varepsilon_0} \int_V \rho d V\) |
2. | \(\oint_S \vec{B} \cdot \overrightarrow{d S}=\frac{m}{\mu_0}\) |
3. | \(\oint_S \vec{E} \cdot \overrightarrow{d l}=-\frac{d}{d t} \int_S \vec{B} \cdot \overrightarrow{d S}\) |
4. | \(\oint_S \vec{H} \cdot \overrightarrow{d S}=\int_C\left(\vec{J}+\frac{d}{d t}\left(\varepsilon_0 \vec{E}\right)\right) \cdot \overrightarrow{d S}\) |
The S.I. unit of displacement current is:
1. | Henry | 2. | Coulomb |
3. | Ampere | 4. | Farad |
1. | \(E_0k = B_0 \omega\) |
2. | If the electric field is in the \(z\text-\)direction then the magnetic field should be in the \(-y\text-\)direction |
3. | Both 1 and 2 are correct |
4. | Only 1 is correct |
1. | \(20\) m | 2. | \(30\) m |
3. | \(40\) m | 4. | \(10\) m |
Which of the following electromagnetic waves has minimum frequency?
1. Radio waves
2. Infrared waves
3. Microwaves
4. X-rays
1. | \(1.873 \times 10^7~\text{V/s} \) |
2. | \(1.873 \times 10^8~\text{V/s}\) |
3. | \(1.873 \times 10^9~\text{V/s}\) |
4. | \(1.873 \times 10^{10}~\text{V/s}\) |
A lamp emits monochromatic green light uniformly in all directions. The lamp is \(3\%\) efficient in converting electrical power to electromagnetic waves and consumes \(100\) W of power. The amplitude of the electric field associated with the electromagnetic radiation at a distance of \(5\) m from the lamp will be:
1. \(1.34\) V/m
2. \(2.68\) V/m
3. \(4.02\) V/m
4. \(5.36\) V/m