How do I make a new object appear by hovering over a different object?

Hey there, I hope this one isn’t too obvious but I am finding myself very stuck.

What I am trying to do, is set up my file so that when I am hovering over an image situated on the left, a different image will appear next to it on the right, and when no longer hovering on the original image, the image on the left would disappear. This is a scrolling page, so would hope that both images would scroll up and down with the page.

Thank you!