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