Textbook brain teaser
A pencil in a glass of water looks bent. What does this reveal about light speed in water compared with air?
پانی میں پنسل مڑی نظر آتی ہے۔ پانی اور ہوا میں روشنی کی رفتار کے بارے میں کیا معلوم ہوتا ہے؟
Solution & explanation
Refraction at the water–air boundary changes ray direction and apparent position. Water has a higher refractive index, so v = c/n is lower than in air. Bending alone shows a speed contrast; use known ray geometry to infer which medium is slower.
Independent study material · English-medium textbook p. 72 · Original book ↗