A frictionless inclined plane is adjusted so that its inclination to the horizontal is equal to the Brewster angle for a transparent material of refractive index 4 ÷ 3 relative to air. A small block is released from rest on the plane. What is the block's acceleration along the incline?
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Question

A frictionless inclined plane is adjusted so that its inclination to the horizontal is equal to the Brewster angle for a transparent material of refractive index 4 ÷ 3 relative to air. A small block is released from rest on the plane. What is the block's acceleration along the incline?

Options

G1 Physics · Accepted Answer

Brewster's law gives tan i(B) = 4 ÷ 3. Therefore we may use a 3-4-5 triangle: sin i(B) = 4 ÷ 5. On a frictionless incline, acceleration along the plane is a = g sin i(B). Hence, a = g(4 ÷ 5) = 4g ÷ 5. Correct option: B.