A 100W electric bulb produces electromagnetic radiation with...

Intensity $= \dfrac{power \times η}{A} . . . \left(1\right)$

We know,

\dfrac{1}{2}$I =$\dfrac{1}{2}{ε}_{0}$E^{2}c$

I = \left(8 . 854 \times {10}^{- 12}\right) \left({2}^{2}\right) \left(3 \times {10}^{8}\right)</p><p>I = 0 . 0106wm^{- 2} . . . \left(2\right)

On substituting \left(2\right) in \left(1\right),~

$0 . 0106 =$\dfrac{100 \times η}{4 \times \pi \times \left({10}^{2}\right)}

$⇒ η = 0 . 133 = 13 . 3$