Okay kiddo, let me explain to you what Cooke triplet is. Cooke triplet is a kind of lens that is used in cameras to help take clear pictures. It is made up of three pieces of glass that are arranged in a special way.
Just like how you use a magnifying glass to make things look bigger, cameras also use lenses to make images look better. Now, each of the three pieces of glass in a Cooke triplet has a different job to do. One piece of glass is thicker in the middle and helps bend light in a specific way. Another piece of glass is thinner and helps prevent any color blurring in the image. The last piece of glass is also thicker but it makes sure that everything in the picture is in focus.
When the Cooke triplet is put together, these three pieces of glass work together to make sure that pictures taken with the camera are clear, sharp and in focus. So, that's what Cooke triplet is all about- a special kind of lens that is made up of three pieces of glass that work together to help take great photos.