How can i make converging rays go in a straight path

Question

Hello sir.

i need a help with my science project.

actually i have used fresnel lens to concentrate sunlight to a point to burn things

so it burning objects when kept at that focus

so i want my rays to have a burning effect to long ranges so what can i do??

Answer 1

the focus is a single point through which all light rays pass. If you want to burn things farther away, you need a lens with a different focal length.