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[tex]\colorbox{cyan}{Answer }[/tex]

Given :

Length of laser beam = 60 cm = 0.6 m

Power = 4 mW = 4 × 10⁻³ W

To find :

Energy stored in the laser

Solution :

We know that, the beam travels with the speed of light = c = 3 × 10⁸

The time taken by the laser beam to travel through 60 cm is,

time = distance / speed

∴ t = [tex]\frac{0.6}{3 . 10^{8} }[/tex] seconds=

∴ t = 2 × 10⁻⁹ seconds

Now, the energy stored in the beam will be given by,

Energy = Power × Time

∴ U = (4 × 10⁻³) × (2 × 10⁻⁹)

∴ U = 8 × 10⁻¹² J

Answer : The energy stored in the beam will be 8 × 10⁻¹² Joules.

Hence, option (1) will be correct.

Explanation:

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