Reflection: you look in the mirror.
Refraction: You put a straw in a glass of water, and it looks like it broke.
Absorption: If you have a black sweater and you wear it out in the cold, the black sweater is going to hold in heat better than a lighter sweater because the black sweater absorbs light .
Mechanical energy (ME) is the sum of potential energy (PE) and kinetic energy (KE). When the toy falls, energy is converted from PE to KE, but by conservation of energy, ME (and therefore PE+KE) will remain the same.
Therefore, ME at 0.500 m is the same as ME at 0.830 m (the starting point). It's easier to calculate ME at the starting point because its just PE we need to worry about (but if we wanted to we could calculate the instantaneous PE and KE at 0.500 m too and add them to get the same answer).
At the start:
ME = PE = mgh
ME = 0.900 (9.8) (0.830)
ME = 7.32 J
A rain gauge! Hope this helps!