Final answer:
When you speak into one can of a makeshift telephone, the sound waves travel through the air, causing the bottom of the can to vibrate. The vibrations are then transferred through the string to the other can, allowing the person at the other end to hear the sound.
Step-by-step explanation:
When you speak into one of the empty cans of a makeshift telephone, the sound you produce travels through the air as sound waves. These sound waves cause the bottom of the can to vibrate. The vibrations are then transferred to the string, which acts as a medium for the sound waves to travel to the other can. The person at the other end of the string can hear the sound because the vibrating bottom of their can creates sound waves that travel through the air and into their ear.
The string needs to be tight in order for the sound waves to travel effectively. If the string is loose, it will absorb some of the energy from the vibrations, making the sound quieter and harder to hear. A tight string allows the vibrations to travel more efficiently, resulting in a clearer and louder sound.