From energy levels to laser light
From energy levels to laser light

A photon is a discrete packet of electromagnetic radiation, and laser action depends on particles having allowed energy levels. When a particle changes level, it absorbs or emits a photon whose energy matches the gap:
Step-by-step lessons on Eduqas A Level Physics Lasers. Each one builds up to exam-style questions. Physics is one of the most mathematically demanding A Levels -- a minimum of 40% of the marks require maths skills at Level 2 (GCSE) standard or above, so build calculation and graph-handling fluency alongside the conceptual content from the start.