47uf is the industry standard "preferred value" - electro caps generally have a VERY wide tolerance range in any case rarely better than 5%
A typical 10% 47uf could actually be anywhere from 37~52 and still be perfectly acceptable.
Usually electro caps are used for bypass applications and the value is not overly critical.
To answer your question, YES, a 47uf is a perfectly acceptable replacement for a 50uf electro cap - just make sure the voltage is the same or HIGHER for the replacement.