Q. No.The magnetic field in a plane electromagnetic wave is given by \(\mathrm{B}=\left(2 \times 10^{-7}\right) \mathrm{T} \sin \left(0.5 \times 10^3 \mathrm{x}+1.5 \times 10^{11} \mathrm{t}\right )\). The wavelength and frequency of the wave are respectively:
1.
\( 2.16 \mathrm{~cm}, 24.1 \mathrm{~GHz} \)
2.
\( 0.29 \mathrm{~cm}, 13.7 \mathrm{~GHz} \)
3.
\( 3.23 \mathrm{~cm}, 20.0 \mathrm{~GHz} \)
4.
\( 1.26 \mathrm{~cm}, 23.9 \mathrm{~GHz}\)
The magnetic field in a plane electromagnetic wave is given by;
\(B_y=\left(2 \times 10^{-7}\right) \sin \left(0.5 \times 10^3 {x}+1.5 \times 10^{11} {t}\right)~\text{T}\).
The expression for the electric field is:
| 1. | \(E_z=60 \sin \left(0.5 \times 10^3 x+1.5 \times 10^{11} t\right) ~\text{V/m} \) |
| 2. | \(E_z=60 \sin \left(1.5 \times 10^3 x+0.5 \times 10^{11} t\right) ~\text{V/m} \) |
| 3. | \(E_z=55 \sin \left(0.5 \times 10^3 x+1.5 \times 10^{11} t\right) ~\text{V/m} \) |
| 4. | \(E_z=55 \sin \left(1.5 \times 10^3 x+0.5 \times 10^{11} t\right) ~\text{V/m} \) |
Assume a bulb of efficiency \(2.5\%\) as a point source. The peak values of the electric field and magnetic field produced by the radiation coming from a \(100~\text{W}\) bulb at a distance of \(3~\text{m}\) are respectively:
| 1. | \( 2.5 ~\text{V/m}, ~2.2 \times 10^{-8} ~\text{T} \) |
| 2. | \( 3.6 ~\text{V/m}, ~ 3.6 ~\text{T} \) |
| 3. | \( 4.07~\text{V/m},~ 1.4 \times 10^{-8} ~\text{T}\) |
| 4. | \( 4.2 ~\text{V/m}, ~3.4 \times 10^{-6}~\text{T}\) |
A capacitor of capacitance \(C\) is connected across an AC source of voltage \(V\), given by;
\(V=V_0 \sin \omega t\)
The displacement current between the plates of the capacitor would then be given by:
1. \( I_d=\frac{V_0}{\omega C} \sin \omega t \)
2. \( I_d=V_0 \omega C \sin \omega t \)
3. \( I_d=V_0 \omega C \cos \omega t \)
4. \( I_d=\frac{V_0}{\omega C} \cos \omega t\)
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 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. | \( a>c>b\) |
| Statement I: | Charged particles which undergo acceleration or deceleration radiate their energy away. |
| Statement II: | Therefore, charged particles moving in circular paths in a uniform magnetic field should also radiate their energy. |
| 1. | Statement I is true, Statement II is true and Statement I implies Statement II. |
| 2. | Statement I is true, Statement II is true and Statement I does not imply Statement II. |
| 3. | Statement I is true, Statement II is false. |
| 4. | Statement I is false, Statement II is true. |
The speed of light depends:
| 1. | on elasticity of the medium only. |
| 2. | on inertia of the medium only. |
| 3. | on elasticity as well as inertia. |
| 4. | neither on elasticity nor on inertia. |
A compass needle is placed in the gap of a parallel plate capacitor. The capacitor is connected to a battery through a resistance. The compass needle:
| 1. | does not deflect. |
| 2. | deflects for a very short time and then comes back to the original position. |
| 3. | deflects and remains deflected as long as the battery is connected. |
| 4. | deflects and gradually comes to the original position in a time which is large compared to the time constant. |
Displacement current goes through the gap between the plates of a capacitor when the charge of the capacitor:
| a. | increases |
| b. | decreases |
| c. | does not change |
| d. | is zero |
Choose the correct option:
| 1. | (a), (b) |
| 2. | (b), (c) |
| 3. | only (c) |
| 4. | (a), (d) |
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