A Laser Having with a Spot 1

question 61

Multiple Choice

A laser having with a spot 1.00 mm in diameter is shone perpendicularly on the center of a thin,perfectly reflecting circular (2.00 mm in diameter) aluminum plate mounted vertically on a flat piece of cork that floats on the surface of the water in a large beaker.The mass of this "sailboat" is 0.0550 g and it travels 3.00 mm in 50.0 s.Assuming that the laser power is constant in the region where the sailboat is located during the experiment,what is the power of the laser used in this demonstration? (Neglect air resistance and the viscosity of the water.)

• A)34.6 mW
• B)25.2 mW
• C)22.7 mW
• D)19.8 mW
• E)15.1 mW