DENJIRO: Today, I’ll show you an experiment using light, which genius scientist Einstein studied and won a Nobel Prize in Physics for. This here is an apparatus made of aluminum foil. It is known as an electroscope, and it detects if something has an electric charge. Let me rub a PVC pipe with a scarf and transfer static electricity to the electroscope. Now that there is an electric charge in the electroscope, the aluminum sheets have opened up. If I touch it with my hand, the electricity escapes, and the sheets fall down. Now I have here two electroscopes. The one on the left has a positive charge while the other has a negative charge. This next experiment is related to the study that Einstein won the Nobel Prize for. What happens if you shine sunlight on electroscopes that have negative and positive charges? Take a look at the experiment.
NARRATOR: We have electroscopes inside a room so they don’t get affected by wind. Using a mirror, we’re going to shine sunlight on them. Let’s see what happens.
BOY: The aluminum sheet closed up for only the negatively charged electroscope.
DENJIRO: What happened was, due to the sunlight, the negative electrons were chased away from the aluminum. As a result, only the aluminum for the electrometer that was negatively charged ended up closing. This phenomenon is known as the photoelectric effect.
However, even if I shine a bright LED light on the electroscope, the aluminum sheets don’t close. But if I use a germicidal lamp, the photoelectric effect takes place, and the aluminum closes. What is the difference between the two lights? Let’s shine the LED light and germicidal lamp on these beads here. You can see that the color of the beads changes only with the germicidal lamp. These beads change color when exposed to ultraviolet rays. That means the germicidal lamp was emitting ultraviolet rays. It was actually Einstein who explained this phenomenon.
Until then, light was thought of as a wave, but Einstein thought of it as particles with energy. The photoelectric effect was taking place due to ultraviolet rays, which have short wavelengths and more energy. Einstein was awarded the Nobel Prize for his work on this subject.
I hope energy will bring you all happiness. Our magic word is "Happy Energy!"