How does focusing coil work in crt tube?

In a CRT (cathode ray tube), the focusing coil is an electromagnet situated around the neck of the tube. When an electric current passes through the coil, it generates a magnetic field that focuses the electron beam emitted from the cathode onto the phosphorescent screen. By adjusting the current, the focusing coil can refine the beam's convergence, ensuring that the electrons strike the screen at a precise point, resulting in a sharp and clear image. This magnetic focusing is crucial for maintaining image clarity and resolution in CRT displays.