Light — Reflection & Refraction

Priya is twelve years old and obsessed with getting the perfect selfie — not with a phone, but with a metal spoon, because curved surfaces make funny reflections.

She holds the back of the spoon up — convex side. Her face stares back — smaller, upright, the whole room visible behind her. She flips it. The hollow concave side now faces her.

She's upside down. She moves it closer — suddenly upright and huge. She steps back — upside down again. She slowly watches herself flip.

Priya's younger brother Rahul drops a pencil into a glass of water and immediately panics.

Priya looks at the glass. The pencil looks bent at the water's surface, as if someone snapped it at the exact point it entered the water.

Rahul pulls it out. The pencil is perfectly fine.

Priya knows that light travels at different speeds in different materials. In air it moves fast, in water it slows down. When it crosses from air into water, that speed change makes it bend. The pencil isn't broken — light coming from the submerged part bends as it exits the water, so your brain places the bottom of the pencil in the wrong position.

Priya's grandfather can't read the newspaper without his glasses anymore. His eyes have lost the ability to bend light strongly enough to focus it onto the retina.

His glasses have lenses that are thicker in the middle than at the edges — convex lenses. Their job: add extra bending power so the focal point shifts back onto the retina.

One afternoon, Priya picks up his glasses and holds them above a patch of sunlight on the floor. She moves them up and down slowly. At a certain height, the scattered sunlight converges into a bright burning dot on the floor. She's found the focal point.

Priya's neighbour is building a periscope to spy on the cricket match visible from the terrace — but she can't go up because it's exam season.

She builds a cardboard tube with two plane mirrors angled at 45°. Light from the match enters the top, bounces off the first mirror, travels down, bounces off the second, and exits sideways into her eye.

The image is clear, right-way-up, same size as reality. Two reflections, two right-angle bends, light has travelled a path it wasn't supposed to. No lenses — just the first law of reflection applied twice.