A hospital uses an ultrasonic scanner to locate tumors in a tissue. What is the wavelength of the sound in a tissue in which the speed of the sound is 1.7 km/s . the operating frequency of the scanner is 4.2 MHz . ( 1 MHz = 10^6 Hz)
A. 4.05 × 10^-4 m
B. 9.05 × 10^-4 m
C. 6.05 × 10^-4 m
D. 4.05 × 10^4 m