Question

When yellow light with a wavelength of 589 nm enters from the air into a transparent plastic body at an inlet angle of 20.0 °, the angle of refraction is 13.3 °. Count

1. refractive index of plastic 
2. wavelength of light in plastic.

Answer 1

1)

$n=\frac{\sin\alpha}{\sin\beta}=\frac{\sin 20.0°}{\sin13.3°}=1.487,$

2)

$\lambda=\frac{\lambda_0}n=\frac{589}{1.487}=396~nm.$