Electromagnetic Radiation with a Wavelength of 471 Nm Appears as Blue

Multiple Choice

Electromagnetic radiation with a wavelength of 471 nm appears as blue light to the human eye.The energy of one photon of this light is 4.22 × $10 ^ { - 19 }$ J.Thus,a laser that emits $1.3 \times 10 ^ { - 2 } \mathrm {~J}$ of energy in a pulse of light at this wavelength produces ________ photons in each pulse.

A) 1.5 × $10 ^ { 19 }$
B) 1.2 × 10^-23
C) 3.2 × $10 ^ { - 17 }$
D) 3.1 × $10 ^ { 16 }$
E) 6.5 × $10 ^ { 13 }$