how to trigger a gameobject when a player/camera look at it?

hi! so i wanna ask, in horror games the trope of looking at a scary image or getting a glimpse of the monster/ghost would trigger it to hide right? how would you go about doing it though? my guess would be using raycast but im not too familiar with it since ive never tried using raycast i would really appreciate your help!

Hey! You can use the methods in this How can I know if a gameObject is 'seen' by a particular camera? - Questions & Answers - Unity Discussions topic. And once your object is seen, you can trigger whatever you want