what can block a radio wave experiments a science with bobert video short

Recall radio waves are very close to cell phone signals on the electromagnetic spectrum. (show again EM spectrum) That gives me an idea for another experiment. If we turn on a radio and surround it with a radio wave blocking material, the sound from the radio has to stop (animation of radio with music signals coming out, thick square around it then music stops) AND if the material can not block radio waves the sound from the radio has to continue Here are a bunch of experiments, (EM disappears) which ones do you think will block radio waves from being received by the radio (circle ones that work, X out ones that do not) Lets try each material and see which ones work plastic box aluminum foil under water kettle with glass lid kettle with metal lid mylar birthday balloon What about holes Looks like aluminum foil would be a great material. But aluminum foil tears easy. what if we get holes in the aluminum foil, can it still effectively block radio sign br, br,