Light, Heat and Sound

Overview

Light, Heat and Sound form a core segment of the upper-primary science syllabus and appear consistently in WB TET Paper II. These topics test a candidate's understanding of basic physical phenomena that children encounter daily—mirrors, lenses, cooking, musical instruments and echoes. The exam expects you to know definitions, laws, simple numerical relationships and real-life applications rather than advanced derivations.

Mastering this topic requires clarity on three fronts: (1) how light travels and bends, (2) how heat moves from one body to another, and (3) how sound is produced, transmitted and perceived. Questions often link concepts to classroom demonstrations or EVS-style scenarios, so always think of practical examples while revising.

Key Concepts

• **Rectilinear propagation of light**: Light travels in straight lines in a uniform medium; this explains shadows, eclipses and pinhole cameras.

• **Reflection**: When light bounces off a surface. The angle of incidence equals the angle of reflection (measured from the normal). Plane mirrors produce virtual, erect and laterally inverted images of the same size.

• **Refraction**: Bending of light when it passes from one medium to another of different optical density. Light bends towards the normal when entering a denser medium and away when entering a rarer medium.