Light - Reflection and Refraction Notes

This chapter explains how light behaves when it strikes a surface or enters a new transparent medium. In board exams, students are usually tested on ray diagrams, sign convention, formula use, and image-formation logic.

The main ideas are reflection by mirrors, refraction through glass and lenses, image properties, and numerical questions using mirror formula, lens formula, and magnification.

Reflection is the bouncing back of light from a polished surface. The two laws of reflection are that the angle of incidence equals the angle of reflection, and the incident ray, reflected ray, and normal lie in the same plane.

Spherical mirrors are of two types: concave and convex. A concave mirror can form real or virtual images depending on object position, while a convex mirror always forms a virtual, erect, and diminished image and is used as a rear-view mirror.

Refraction is the bending of light when it passes obliquely from one medium to another because its speed changes. Light bends towards the normal while going from a rarer medium to a denser medium, and away from the normal in the reverse case.

A convex lens is a converging lens and can form real or virtual images depending on object position. A concave lens is a diverging lens and always forms a virtual, erect, and diminished image.

Students should practise labelled ray diagrams for concave mirror, convex mirror, convex lens, and concave lens carefully because diagram questions are among the most repeated in Class 10 Science.

The biggest mistakes are mixing mirror and lens formulas, using the wrong sign convention, and not stating image nature clearly as real or virtual, inverted or erect, enlarged or diminished.