What type of energy is needed to get a reaction started?

Asample of silver (with work function ? = 4.52 ev) is exposed to an ultraviolet light source (? = 200 nm), which results in the ejection of photoelectrons. what changes will be observed if: silver is replaced with copper (? = 5.10 ev) more photoelectrons ejected no photoelectrons are emitted fewer photoelectrons ejected more energetic photoelectrons (on average) less energetic photoelectrons (on average)

How heavy is thanos? a) 3000 lbs b) all of it c) the price of tea in china d) heavy enough

What is a metal replacement reaction