What experiments were done to prove that this law is true?

To provide you with a detailed answer, I would need to know which specific law you are referring to, as "this law" could refer to many different laws in scientific contexts, such as Newton's Laws of Motion, the laws of thermodynamics, laws of genetics, etc. Each of these laws has its own set of experiments and evidence supporting them. Please specify the law you are interested in, and I'll be happy to help with the relevant experiments and proofs!