I have internet and an imac. Possible to wirelessly connect imac to a TV in the house?

Good, then really all you need is an Apple TV HD or Apple TV 4K and you should be in business. Without one, what you want to do is not possible. Please refer to https://www.apple.com/airplay/ and for more detailed information https://en.wikipedia.org/wiki/AirPlay

Your TV must have an HDMI input to be able to connect to the Apple TV, considering the age of the TV it may or may not have that so please check your TV before buying an Apple TV.

You would need an Apple TV HD or 4K model to wirelessly display computer content on the TV. Please navigate to www.apple.com/tv and review the 2 models. You would be using Airplay to view the computer content on the TV.

You will learn that an Apple TV is FAR more capable than just using the Airplay feature. In order to do this you will need a strong wireless network and have great signal throughout your home.

You have left us short on information with which to help:

1) What iMac sub-model and what macOS version (both from "About this Mac..." in your Apple menu)/

2) Do you have a wireless access point in you house?

3) Is the TV a "smart" TV that can access a wireless signal (older ones cannot).

4) Do you use a "set top" box like an Apple TV or a Roku?

We'd love to help but we are your fellow end users, not Apple, and must rely on you for your equipment's specifications.

Your welcome.