Question 3.2
Calculate the value of critical angle for light passing from glass to air (given that refractive index of
glass - 1.5)

42°

Explanation:

From the question given above, the following data were obtained:

Refractive index (n) = 1.5

Critical angle (C) =?

The refractive index and the critical angle are related according to the following reaction:

n = 1 / Sine C

Thus, with the above formula, we can obtain the critical angle as follow:

Refractive index (n) = 1.5

Critical angle (C) =?

n = 1 / Sine C

1.5 = 1 / Sine C

Cross multiply

1.5 × Sine C = 1

Divide both side by 1.5

Sine C = 1 / 1.5

Sine C = 0.6667

Take the inverse of sine

C = Sine¯¹ (0.6667)

C = 41.8 ≈ 42°

Thus, the critical angle is approximately

42°.

second mirror gathers light from a faraway object and reflects it to another mirror. - a.

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