To show the photoelectric effect in a simple lab experiment, students can follow these easy steps. Let’s break it down!

What You Need:

1. Light Source: A light that can change frequencies, like a UV lamp or a special light that gives one color.
2. Metal Plate: A metal like zinc or potassium that can give off electrons when exposed to light.
3. Electrometer: A tool that measures electric current.
4. Power Supply and Circuit: These will help create the necessary energy to run the experiment.
5. Vacuum Chamber: This keeps air out so it doesn't affect the results.

Steps of the Experiment:

1. Setup: Place the light source so it shines on the metal plate, which is connected to the electrometer.
2. Change Frequency: Start with a low frequency light (like red) and slowly switch to higher frequency lights (like blue or UV).
3. Measure Current: At each light frequency, check how much current is produced by the electrons using the electrometer.

What You Will Notice:

• Threshold Frequency: You’ll see that no current flows until the light reaches a certain frequency. This is called the threshold frequency. It shows us that light acts like tiny packets of energy called photons, not just a smooth wave.
• Current Increase: After hitting the threshold frequency, if you make the light brighter (more photons), more electrons will come out; this means the current increases. But if you change to a higher frequency without changing brightness, the energy of the released electrons gets higher. This proves that light has particles as well.

A Simple Formula:

Einstein came up with a formula to explain this. It says:

$K.E. = hf - \phi$

In this formula:

• $K.E.$ is the energy of the electrons,
• $h$ is a special number (Planck's constant),
• $f$ is the frequency of the light,
• $\phi$ is the energy needed to release the electrons from the metal.

Why This Matters:

This experiment is super important because it helps us understand the quantum view of light and matter. It’s a key concept for modern physics and quantum mechanics! Students will get to see firsthand how science moved from classical physics to the exciting world of quantum theory.