7.42 A team of scientists is designing a radar as a probe for measuring the depth of the ice layer over the antarctic land mass. In order to measure a

detectable echo due to the reflection by the ice-rock boundary, the thickness of the ice sheet should not exceed three skin depths. If & = 3 andE" = 10-2 for ice and if the maximum anticipated ice thickness in the area under exploration is 1.2 km, what frequency range is use able with the radar?