Question

A point source of electromagnetic radiation has an average power output of $1500 \,W$. The maximum value of electric field at a distance of $3\,m$ from this source in $ V{{m}^{-1}} $ is

• A. 500
• B. 100
• C. $ \frac{500}{3} $
• D. $ \frac{250}{3} $
• E. $ 10\sqrt{5} $

Answer 1

Answer: (B)

$ {{E}_{0}}=\sqrt{\frac{{{\mu }_{0}}c{{P}_{av}}}{2\pi {{r}^{2}}}}=\sqrt{\frac{(4\pi \times {{10}^{-7}})\times (3\times {{10}^{8}})\times 1500}{2\pi \times {{(4)}^{2}}}} $ $ =100V{{m}^{-1}} $