The phrase "false notion" means to have a mistaken or incorrect belief about something.
Sentences with «false notion»
The world is eager to offer him an onslaught of false notions of what it means to be a man, and to confuse her about what it means to become a woman. (christianhomeschoolmoms.com)
That will only lead you to false notions about me. (nakedpastor.com)
But don't limit this to religion only, learn about false notions regarding atheists also. (religion.blogs.cnn.com)