Indicate Which of the Following Sources Produces the Lowest Energy $\lambda$

Multiple Choice

Indicate which of the following sources produces the lowest energy photons.

A) a radio station with v = 106.7 MHz
B) a dentist's X-ray source with $\lambda$ = 100 pm
C) the laser in a CD player with $\lambda$ = 650 nm
D) a microwave oven with v = 6.0 * 10¹⁰ Hz
E) your cell phone with v = 1.750 GHz