Greeetings, yesterday I had to do the attached assignment but I ran into a problem. It is not so much about how to solve the exercise but rather about how to approximate the term:(adsbygoogle = window.adsbygoogle || []).push({});

r_{+}-r_{-}

My solutions notes writes this as:

r_{+}-r_{-}= Lx/z_{0}

Is it just me or is there something wrong with this expression: How did my teacher arrive at that from:

r_{+}-r_{-}= √((x-L/2)^{2}+y^{2}+z_{0}^{2}) - √((x+L/2)^{2}+y^{2}+z_{0}^{2})

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# Homework Help: Spherical wave

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