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 10. Speed, Wavelength, Frequency and the Doppler effect IGCSE Waves (Live) Complete & Continue Next Lesson Learn More 7. Diffraction