Is it normal to sometimes hear and see things that aren't there?

Seldom, though it's picking up recently, I hear and see things that aren't there.

For example:
I have seen the flashing lights of a police car while driving home with my sister. I thought I saw it in the distance but nope. My sister didn't see it either...

When getting a drink in a dimly lit room, I thought I saw a man approaching me and I jerked away and gasped.

Sometimes I hear my name being whispered to me when no one is saying it.

When home alone I sometimes hear the doorknob jostling when no one is there.