A krypton laser produces a cylindrical red laser beam 3.0 mm in diameter with 4.0 W of power. What is the light intensity on a wall 5.0 m away from the laser?
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We are not given the beam divergence, so we must assume the beams stays 3.0 mm in diameter (0.0015m radius) at any given distance.
So the intensity is 4.0W / (pi*0.0015m)^2 = 566kW / m^2 at any distance, including 5m away.
Yes, the area is just the cross-sectional area of the beam, because the laser is a uni-directional light source.
So area A = pi*r^2, and Intensity = Power / Area as calculated above.
So the intensity is 4.0W / (pi*0.0015m)^2 = 566kW / m^2 at any distance, including 5m away.
Yes, the area is just the cross-sectional area of the beam, because the laser is a uni-directional light source.
So area A = pi*r^2, and Intensity = Power / Area as calculated above.
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4.0w