[单选题]
When a beam of light (wavzre6.dm) v(i uelength = 590 nm), originally traveling in air, entero+qt de. zzc9j6z +(qos a piece of glass (index of refqdzjzet.+( 9q +o 6oczraction 1.50), its frequency
A. increases by a factor of 1.50.
B. is reduced to 2/3 its original value.
C. is unaffected.
D. none of the given answers