A sonar sound wave is emitted from a research vessel and reflects off a flat, horizontal seabed. Which statement correctly describes this reflection?

• A: The angle of reflection is measured between the reflected wave path and the horizontal seabed.
• B: The angle of incidence is equal to the angle of reflection, with both angles measured relative to the normal to the seabed.
• C: The reflected wave always travels at a higher speed than the incident wave.
• D: The angle of incidence is measured between the incident wave path and the horizontal seabed.

A ray of light passes from air into a beaker filled with pure glycerol. The angle of incidence $i$ is $58^{\circ }$ and the angle of refraction $r$ is $35^{\circ }$.

State the name of the line drawn perpendicular to the surface of the glycerol at the point where the light ray enters.

State the relationship between the refractive index $n$ of the liquid, the angle of incidence $i$ in air, and the angle of refraction $r$ in the liquid.

Calculate the refractive index of glycerol. Give your answer to 2 decimal places.

Inside a pair of binoculars, glass prisms are used to reflect light rays by $90^{\circ }$ or $180^{\circ }$ without any light escaping through the back faces of the prism.

State the name of the physical phenomenon that allows light to be completely reflected at these internal boundaries.

Explain the two conditions required for this phenomenon to occur at the boundary inside the prism.