Question

exam 1: atomic theory/structure
which of the following observations led thomson to conclude that cathode - ray particles were negatively charged?
he observed that cathode - ray particles traveled in a straight path through electric fields.
he observed that positively charged plates repelled the rays.
he observed that negatively charged plates repelled the rays.
he observed that a metal plate exposed to cathode particles became positively charged.

Explanation:

Like - charges repel. If negatively - charged plates repelled cathode rays, they must be negatively charged.

Answer:

He observed that negatively charged plates repelled the rays.