Physical Layer is responsible for the communication of the unstructured raw data streams over a physical medium.
Explanation: Physical Layer maintains the date rate (how many bits a sender can send per second). It performs Synchronization of bits. It helps in Transmission Medium decision (direction of data transfer).
Physical layer of OSI model is the first layer. This layer deals with most of the network’s physical connections - wireless transmission, cabling, cabling standards and types, connectors and types, network interface cards, and more - as per network requirements. However, the physical layer does not deal with the actual physical medium (like copper, fiber).