Electromagnetic waves and its nature

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Question

The energy stored in a 90 cm length of a laser beam operating at 10 mW is $_________\times 10^{- 12} J$

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Solution

Time taken by laser beam to move through a distance 90 cm is, $t = \frac{90}{C}$
$t = \frac{90 c m}{3 \times 10^{10} c m / s} \Rightarrow t = 30 \times 10^{- 10} s$
The energy contained in $90 c m$ length of laser beam is
$U = p o w e r \times t i m e = 10 \times 10^{- 3} \times 3 \times 10^{- 9} J$

So, $U = 30 \times 10^{- 12} J$

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Electromagnetic waves and its nature

Remember concepts with our Masterclasses.

The energy stored in a 90 cm length of a laser beam operating at 10 mW is _________×10−12J

Time taken by laser beam to move through a distance 90 cm is, t=90C t=90cm3×1010cm/s ⇒t=30×10−10s The energy contained in 90 cmlength of laser beam is U=power× time=10×10-3×3×10−9 J So, U=30×10−12J

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The energy stored in a 90 cm length of a laser beam operating at 10 mW is $_________\times 10^{- 12} J$