Alex was a curious young kid who loved inventing things. One day, he became really interested in radios. He wanted to know how they worked and how they could send and receive signals through the air. So, he decided to visit Heinrich Hertz, an old German physicist, who was famous for his experiments with electromagnetic waves.

When Alex arrived at Hertz's house, he found him in his laboratory full of strange gadgets. Hertz was happy to see a young mind eager to learn. Alex asked him, 'How do radios send and receive signals?' Hertz smiled and said, 'Let me show you with a simple example.'

Hertz took out a small rope and asked Alex to hold one end. He then held the other end and started moving it up and down really fast. Alex noticed that each time Hertz moved his end of the rope, it created ripples that traveled through the rope to Alex's hand.

Hertz explained, 'Just like these ripples travel through the rope, radios send and receive waves called radio waves. These waves can go through the air and carry signals, just like the ripples carry energy through the rope.' Alex was amazed by this simple yet fascinating explanation.

Hertz continued, 'To send signals, radios use an antenna to generate radio waves. These waves travel through the air and can be picked up by other radios with antennas. That's how radios can communicate with each other.' Alex couldn't wait to try it out himself.

Hertz showed Alex some different types of antennas and explained that each one could send and receive signals on specific frequencies. He said, 'Think of it like different channels on a TV. Radios can tune in to different frequencies to listen to different stations.' Alex found this comparison really helpful.

Hertz also told Alex that radio waves could travel really long distances, even across oceans. He said, 'When the waves reach their destination, a radio can convert them back into sound or pictures. That's how we can hear music or news from far away.' Alex couldn't believe how magical radios were.

Alex thanked Hertz for the amazing lesson and left his laboratory feeling inspired. He couldn't wait to share his new knowledge with his friends and maybe even invent his own radio someday. From that day on, Alex became even more curious about the wonders of science.