At what angle should the beam fall on the glass for the refracted beam to be perperdicular to the reflected one?

n = 1.6;
A + B = 90 degrees.
You need to find a.
We use the well-known formula:
n = sinA / sinB.
Let’s transform it.
n = sinA / sin (90-a) = sinA / cos A = tg A.
Find the corner:
a = arctgn = arctan 1.6 = 58 degrees.
Answer: 58

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