Practicing Success
About 6% of the power of a 100 W light bulb is converted to visible radiation. The average intensity of visible radiation at a distance of 8 m is (Assume that the radiation is emitted isotropically and neglect reflection.) |
$3.5 × 10^{-3} Wm^{-2}$ $5.1 × 10^{-3} Wm^{-2}$ $7.2 × 10^{-3} Wm^{-2}$ $2.3 × 10^{-3} Wm^{-2}$ |
$7.2 × 10^{-3} Wm^{-2}$ |
Here, power of bulb = 100 W As intensity, I = $\frac{\text { Power of visible light }}{\text { area }}=\frac{100 \times 6 / 100}{4 \pi(8)^2}=7.2 × 10^{-3} Wm^{-2}$ |