12-109.An interference pattern using microwaves of wavelength 3.0 cm is set up in a physics laboratory. (Microwaves are part of the electromagnetic spectrum; they travel at a speed of 3.0X10⁸ m/s in air.) Two sources of in-phase waves are placed 18 cm apart and a receiver is located 4.8 m away from the midpoint between the sources.

(a) What is the frequency of the microwaves? Express your answer in megahertz (MHz) and gigahertz (GHz).

.(b) As the receiver is moved across the pattern parallel to an imaginary line joining the sources, what is the distance between adjacent maxima, between adjacent minima, and between a maximum and an adjacent minimum?

[Ans. (a) 10000 MHz; 10 GHz (b) 0.80 m; 0.80 m; 0.40 m]

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The correct relationship to solve part (a) is: