Question

A glass prism ABC (refractive index 1.5), immersed in water (refractive index 4/3). A ray of light is incident normally on face $AB$ . If it is totally reflected at face $AC$ then

• A. $sin \theta \geq \frac{8}{9}$
• B. $sin \theta \geq \frac{2}{3}$
• C. $sin \theta = \frac{\sqrt{3}}{2}$
• D. $\frac{2}{3} < sin \theta < \frac{8}{9}$

Answer 1

Answer: (A)

For total internal reflection at $AC$ face
$sin i \geq \frac{\mu _{w}}{u_{g}}$
$sin \theta \geq \frac{4}{3 \times 1.5}$
$sin \theta \geq \frac{8}{9}$