About $20 \%$ of the power of a $100 \ W$ bulb is converted to visible radiation. Assuming that the radiation is emitted isotropically and neglecting reflection,the average intensity of visible radiation at a distance of $5 \ m$ is $\frac{\alpha}{25 \pi} \ W/m^2$. The value of $\alpha$ is

The electric field in an electromagnetic wave is given by $E = 56.5 \sin \omega(t - x/c) \; NC^{-1}$. Find the intensity of the wave if it is propagating along the $x$-axis in free space. (Given $\varepsilon_{0} = 8.85 \times 10^{-12} \; C^{2} N^{-1} m^{-2}$ and $c = 3 \times 10^{8} \; m/s$)

For a transparent medium,the relative permeability $\mu_{r}$ and relative permittivity $\epsilon_{r}$ are $1.0$ and $1.44$ respectively. The velocity of light in this medium would be,

$A$ 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 nearly.......$V/m$

The frequency of an electromagnetic wave is $3 \, MHz$. If the refractive index of the medium is $n = 4$,what happens to the wavelength and frequency when it passes through the medium?

For an electromagnetic wave propagating through vacuum, $\vec{k}$, $\vec{E}$, and $\omega$ represent the propagation vector, electric field, and angular frequency, respectively. The magnetic field associated with this wave is represented by: