Progress IGCSE Waves (Live) Complete & Continue Next Lesson Learn More 1. What is a Wave? 2. Electromagnetic Waves 3. Reflections 4. Refraction 5. Total internal reflection 6A. Lenses (Part 1) 6B. Lenses (Part 2) 7. Diffraction 8. Sound 9. Ultrasound IGCSE Waves (Live) Complete & Continue Next Lesson Learn More 5. Total internal reflection