Determine the amount of energy carried in l.0 m of a 3.5-mW He-Ne laser beam if the cross-sectional area of the beam is 5.0 x 10^-6 m². A)0.012 J B)4.1 x 10^-⁸ J C)1.2 x 10^-¹¹ J D)1.0 J

Question

Quizplus · Accepted Answer

We can use the formula: 
Energy = Power x Time 
to determine the amount of energy carried in a certain distance. In this case, we are given the power (3.5 mW) and need to find the energy carried in 1.0 m of the beam.

First, we need to convert the power to SI units: 
3.5 mW = 3.5 x 10^-3 W

Next, we can use the formula: 
Energy = Power x Time = Power x Distance/Speed of light

where the speed of light is approximately 3.0 x 10^8 m/s.

Plugging in the values: 
Energy = (3.5 x 10^-3 W) x (1.0 m) / (3.0 x 10^8 m/s) x (5.0 x 10^-16 m^2) 
Energy = 1.17 x 10^-11 J

This is closest to choice C, 1.2 x 10^-11 J, which is the best answer.

Determine the Amount of Energy Carried in L