Assume the helium-neon lasers commonly used in student physics laboratories have power outputs of 0.250 mW. (a) If such a laser beam is projected onto a circular spot 2.50 mm in diameter, what is its i
a) 0.159 mW/cm²
b) 1.59 mW/cm²
c) 15.9 mW/cm²
d) 159 mW/cm²