Question

27. Given that the refractive index of a glass slab is 1.5, four observations were made by tracing the path of a ray of light passing through it for an angle of incidence 40. The observed measures of the angle of refraction were18, 22, 25 and 30, respectively. Which of these observations are correct?

Answer 1

all the observations were correct

Answer 2

Answer: 25

Explanation:

Refraction occurs when light enters from one medium to another. The light bends towards or away from the normal. It is governed by Snell's law:

$\frac{\text{sin i}}{\text{sin r}}=\frac{n_2}{n_1}$

In the given situation, light enters from air to glass slab. The refractive index of air n₁ = 1.0

The refractive index of glass slab, n₂ = 1.5

Angle of incidence, i = 40⁰

Thus, angle of refraction, r is:

$\frac{sin 40^o}{\text{sin r}}=\frac{1.5}{1}\\ \frac{0.64}{1.5} = \text{sin r}\\ \Rightarrow \text{sin r}= 0.428\Rightarrow r = 25^o$

Thus, the correct reading of the angle of refraction is 25.