See below for many resources on this topic. Let me know if they are helpful, and if you have others to add to the list.
Waves and sound
Sounds Amazing, a resource for GCSE Physics (exams taken in the UK, usually at around 16 years old).
Simple wave simulator from physicsclassroom.com
Video of homemade wave machine http://thekidshouldseethis.com/post/how-to-build-your-own-wave-machine-physics-demo
http://thekidshouldseethis.com/post/spinning-daggers-wooden-zoetrope-sculptures-spin-in-the-forest
Visualising sound waves (very cool) http://thekidshouldseethis.com/post/82296107912
Octobass on The Kid Should See This
Multilayered mechanized music making – using old vinyl records on a turntable and many other electronic and mechanical items.Again from The Kid Should See This.
Video of an opera singer and beat boxer under MRI scanner http://www.youtube.com/watch?amp;v=HhRn7E1LaLs
Vocal cords up close while singing http://www.youtube.com/watch?v=-XGds2GAvGQ
Voice change in boys on kidshealth.org: here and here.
The Electromagnetic Spectrum
GCSE Bitesize activity with Geordie voiceover. Probably best for children who prefer auditory or visual learning styles.
Largely text-based explanation from NASA on missionscience.nasa.gov , or here (Flash)
These activities on amazingspace.org are slightly more interactive but still require reading . There is a lesson plan here.
Light and UV light
Corals fluorescing under different lighting conditions
http://thekidshouldseethis.com/post/20471183447
Why is the sky blue? (We didn’t cover this in our first two classes but touched on it in the third class.)
Reflection and refraction: A Rube Goldberg machine on The Kid Should See This.