A simple starter I often used when introducing the topic of light with year 8 was to give them a problem to solve:
I gave no clues but let them use their imaginations (and hopefully a little science knowledge) to come up with a suitable plan. Inevitably, they came up with some interesting ideas but usually understood that in order to see the bone, the dog would have to use reflection.
A research group has now come up with a more elegant, albeit slightly more complicated, solution using laser scattering. The video below shows you how the technique works.
They don’t see this being used by dogs in order to locate bones hidden behind walls but it could be very useful for military and clean-up operations where objects are in dangerous or inaccessible areas.
This could be used for a high ability GCSE group when teaching about reflection, or when discussing the wave/particle nature of light with A-level physics students. It uses the same kinds of technique as ultrasonic testing so could be used as a nice plenary if teaching about this. The technique also relies on the camera being able to record images extremely quickly (every 2 picoseconds, the time it takes light to travel 0.6 mm). This gives students an appreciation of how fast light travels and how the speed equation can be used.
The article on this from Scientific American.