About $5\%$of the power of $100 \mathrm{W}$ light bulb is converted to visible radiation. What is the average intensity of visible radiation at a distance of $10 \mathrm{m}$? Assume that the radiation is emitted isotropically and neglect reflection.

• Correct answer
  A

  $4\times {10}^{-3} \mathrm{W} {\mathrm{m}}^{-2}$

   
• B

  $5\times {10}^{-3} \mathrm{W} {\mathrm{m}}^{-2}$
• C

  $6\times {10}^{-3} \mathrm{W} {\mathrm{m}}^{-2}$

   
• D

  $7\times {10}^{-3} \mathrm{W} {\mathrm{m}}^{-2}$

   

Hence, the correct answer is option: 'A'.