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Question: Answered & Verified by Expert
A laser beam is operating at $100 \mathrm{~mW}$. The amount of energy stored by $90 \mathrm{~cm}$ length of this laser beam will be
PhysicsElectromagnetic WavesTS EAMCETTS EAMCET 2018 (05 May Shift 1)
Options:
  • A $2 \times 10^{-10} \mathrm{~J}$
  • B $3 \times 10^{-10} \mathrm{~J}$
  • C $8 \times 10^{-11} \mathrm{~J}$
  • D $6 \times 10^{-11} \mathrm{~J}$
Solution:
1977 Upvotes Verified Answer
The correct answer is: $3 \times 10^{-10} \mathrm{~J}$
Energy of LASER beam,
$=\frac{I l}{C}=\frac{100 \times 10^{-3} \times 90 \times 10^{-2}}{3 \times 10^8}=3 \times 10^{-10} \mathrm{~J}$

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