Physics Optics Interference

[kirpal_06391]

Q. A radar antenna is located atop a high cliff on the edge of a lake operates at a wavelength of 400m. A parallel beam of electromagnetic wave is received by the antenna at E. One ray directly comes to E and other along the path ABE (after reflection at the water surface) the first minimum is recorded when the angle ABF = 35˚. Find the height of the cliff.

Solution has been attached as PDF file.

Now, my real question is, that whether my solution is correct or not, as my teacher has declared it incorrect but I have VERY STRONG feeling that its correct.

Answer given by my teacher is 349 meters.

 

[kirpal_06391]

Er.. opinions required before Monday

 

[Stonebridge]

On a quick look, the method and answer in the pdf file seem fine.

 

[kirpal_06391]

Well I need either perfectly correct or incorrect type opinion b'coz I'm going to challenge my teacher on that basis