In an introductory lesson on waves, I explained to the class that
long waves can pass around objects, whereas short waves cannot.
I picked up a hat, held it between me and one of the boys and
asked him, "Can you see my face?".
"No, sir", he said.
"Can you hear me?"
"Yes, sir."
"What does that show?" I asked, expecting some answer to the effect that
light waves were short and sound waves were long.
But the boy went for a deeper truth. "You are talking through your hat, sir."
he said.