Physics Question? Need help ASAP please!?

[larkinfan11]

I am having extreme difficulty with the question below. The wavelength should be 2 x .42cm= .84cm which is equal to .0084cm. When using this in the f=v/wavelength equation (f=3.0E8/.0084m) an answer of 3.57E10 Hz is obtained, but I'm being told that this answer is incorrect. Am I missing something? Any Help would be appreciated. Here's the question:

Section 17.5 deals with transverse standing waves on a string. Electromagnetic waves also can form standing waves. In a standing wave pattern formed from microwaves, the distance between a node and an adjacent antinode is 0.42 cm. What is the microwave frequency?

[Steve]

I think the distance between a node and an ADJACENT anti-node is only 1/4 the total wavelength, making the wavelength 4*.42 cm = .0168 m.

Then, f = 3E8/.0168 = 1.785E10 Hz