The index of refraction of this liquid will be 1.28. It is found as the ratio of the sin of the angle of incidence and the angle of reflection.
The refractive index of a substance is a dimensionless quantity that specifies how quickly light passes through it in optics.
The given data in the problem is;
Angle of incidence (i)= 65°
Angle of refraction(r) = 42°
The formula for the index of refraction is;
[tex]\rm n = \frac{sin \ i }{sin \ r} \\\\ \rm n = \frac{sin 65 ^0}{sin 42^0} \\\\ n=1.28[/tex]
Hence, the index of refraction of this liquid will be 1.28.
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