Total internal reflection. i. is a phenomenon of refraction of light. ii. occurs when light rays travel into a…

Analyze the question: We need to decide which statements about total internal reflection (TIR) are correct.

Concept: Total internal reflection happens when light travels from a denser medium to a less dense medium (e.g., glass to air) and the angle of incidence in the denser medium is greater than the critical angle. All the light is then reflected back into the denser medium, and none is refracted out.

Checking each statement:

• i. It is a phenomenon of refraction of light. Correct in the WASSCE context. TIR is treated as a special case that arises when light attempts to pass from one medium to another, and the refraction at the boundary reaches its limit (refracted angle 90° at the critical angle). It is studied under refraction.
• ii. It occurs when light rays travel into a denser medium. Wrong. TIR needs light to travel from a denser medium into a less dense (rarer) medium. Going into a denser medium bends the ray toward the normal, so TIR cannot happen.
• iii. It occurs when the critical angle is just exceeded. Correct. Once the angle of incidence is greater than the critical angle, TIR occurs.
• iv. It is a phenomenon of reflection of light. Correct. The light is entirely reflected back into the original medium, so it is also a reflection phenomenon.

So the correct statements are i, iii and iv.

Tip: Remember "Dense to Rare, Exceed the Angle." TIR needs (1) light going from a denser to a rarer medium, and (2) an angle of incidence greater than the critical angle. If an option says light goes into a denser medium, eliminate it immediately.