Hi, first time posting, nice forums :) Recently in my preparation for my scholarship exams later this year, i was approached by a question which has me rather confused. Im not neccesarily asking for the final definate answer, but it would be nice for some help on how to approach the problem. Radio waves of frequency 600kHz are recieved at a location 10Km from the transmitter. The radio reception temporarily fades due to the interference between the direct beam and that reflected without phase change from a horizontal layer of charged particles formed in the atmosphere by a passing plane. Calculate the minimum height of the plane formulas suggested were λ = dx/L and dsinθ = mλ p.s how do you draw the symbols ?