Which wave requires a physical medium through which to travel?

All mechanical waves require a physical medium through which to travel.  If there isn't any, then mechanical waves don't travel.

Mechanical waves are the waves where physical particles are doing the waving.  They include sound waves, ocean waves, ripples on a pond, clarinet waves, Slinky waves, guitar-string waves, rope waves, etc.  

beta is electron from nucleus

something from nucleus has changed, but charge must be same for cons of charge

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