A Ruby Laser Can Deliver a 4

Multiple Choice

A ruby laser can deliver a 4.33-J pulse in approximately 50 nanoseconds.The wavelength of the light is 694 nm.At least how many atoms within the ruby rod had to be excited to allow this high-energy laser pulse? (h = 6.63 × 10−³⁴ J⋅s,c = 3.00 × 10⁸ m/s,1 eV = 1.6 × 10−¹⁹ J,and 1 nm = 10−⁹ m)

A) 3.5E+18
B) 3.0E+17
C) 1.5E+19
D) 1.5E+21
E) ​1.1E+18