2301nsc Electromagnetism And Optics Show That The Skin Depth For Cu At 5 1015 Hz Mid 4081464
(i) Show that the skin depth for Cu at 5×1015 Hz (middle of the visible light band) is
approximately 1 nm, compared to 10 mm at 50 Hz (AC mains frequency). (4 marks)
(ii) Show that for Cu the limit s e? ? corresponds to 18 f 010 Hz , meaning that this
approximation applies at frequencies up to at least the ultraviolet. (3 marks)
(iii) Show that for Cu at 1.0 MHz the ratio of the wavelength inside to that outside the
conductor (air or vacuum) is 1.41×10–6
. (2 marks)
(iv) Calculate the skin depth for steel at 50 Hz. (2 marks)
(v) If you want to prevent 50-Hz electromagnetic radiation from affecting a sensitive
electronic instrument, is it better to make the case of copper or steel? Explain your answer. (4
marks)
(vi) Mirrors are generally made by coating silver onto glass. Would coating iron onto glass
also make a good mirror? Explain your answer. (3 marks)
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