Total Internal Reflection in Light Transmission

Steps:

• Recall total internal reflection (TIR) occurs when light hits a boundary at an angle greater than the critical angle, reflecting entirely within the medium.
• Identify devices that rely on light guiding without loss through TIR.
• Evaluate each option: magnifying glass uses refraction to bend light; optical fibre traps light via TIR for transmission; enlarger and projector use lenses for image projection via refraction.
• Confirm optical fibre as the match for TIR application.

Why B is correct:

• Optical fibres use TIR to guide light signals along the core by reflecting rays at the core-cladding boundary when the incidence angle exceeds the critical angle, per Snell's law.

Why the others are wrong:

• A: Magnifying glass relies on refraction through a convex lens to enlarge images.
• C: Photographic enlarger uses refraction in lenses to project and magnify negatives.
• D: Projector employs refraction via objective lenses to focus and enlarge light onto a surface.

Final answer: B