Question: I am a 10 year experienced ruby developer, I want to work in blockchain which language will I have to learn
As Ruby (widely used for Rails development) is not used directly for Blockchain development. You will have to learn a language which is more compatible with Blockchain development. i.e. Solidity, Golang, C++ Or Node.js
So, you will likely need to learn Solidity for developing smart contracts on the Ethereum blockchain.
Solidity is not the only language used in blockchain development, but it is the most widely used for smart contract development on the Ethereum platform. Other blockchain platforms may use different languages, such as Golang for the Hyperledger Fabric blockchain, or C++ for the EOS blockchain.
While your experience with Ruby will not directly translate to Solidity or other blockchain languages, your existing programming knowledge and experience should help you learn and adapt quickly. You may want to start by studying Solidity‘s syntax, data types, and control structures, as well as its specific features related to blockchain development such as interacting with the blockchain, managing transactions and handling errors.