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. | \( 4.2 ~\text{V/m}, ~3.4 \times 10^{-6}~\text{T}\) |
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. | \( 1.26 \mathrm{~cm}, 23.9 \mathrm{~GHz}\) |
1. | cannot be less than 1. |
2. | equals 1, always. |
3. | cannot be greater than 1. |
4. | can be any non-zero value. |