Is there a light version of adobe photoshop?

Older versions.
CS4 to CS6; CC 2015 requires around 1 GB of RAM.

It just depends on what "light" means.
If it means something that can be run smoothly on lower-end devices with 4 GB of memory and an entry-level processor, then the newest versions might run and could process very small images; smaller than 500 x500 pixels with less than 10 basic layers. Editing straight out of camera RAW or JPEGs could be a struggle.

Just check the minimum system requirements.

The latest version is Photoshop Elements 2018 and it costs around $100: Amazon.com: Adobe Photoshop Elements 2018: Software