Suppose you went bowling, but instead of a bowling ball you rolled a ping pong ball down the alley. What
do you think would happen?
2. Suppose you rolled a lot of ping pong balls at the bowling pins. Do you think that would change the results
of your experiment? Explain.
Gizmo Warm-up
The phot...
Student Exploration: Photoelectric Effect
Directions: Follow the instructions to go through the simulation. Respond to the questions and
prompts in the orange boxes.
Vocabulary: electron volt, frequency, photoelectric effect, photon, photon flux, voltage, wavelength, work
function
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
1. Suppose you went bowling, but instead of a bowling ball you rolled a ping pong ball down the alley. What
do you think would happen?
It would be very difficult to get the ball to hit the pins, let alone drop them do to its inferior
weight.
2. Suppose you rolled a lot of ping pong balls at the bowling pins. Do you think that would change the results
of your experiment? Explain.
I would imagine that with a significant amount of ping pong balls you would be able to move
the pins.
Gizmo Warm-up
The photoelectric effect occurs when tiny packets of light, called
photons, knock electrons away from a metal surface. Only
photons with enough energy are able to dislodge electrons.
In the Photoelectric Effect Gizmo, check that the Wavelength is
500 nm, the Photon flux is 5 γ/ms, the Voltage is 0.0 volts, and
Potassium is selected. Click Flash the light to send photons of
light (green arrows) toward a metal plate encased in a vacuum
tube.
1. The blue dots on the metal plate are electrons. What happens when the photons hit the electrons?
The electrons detach from the plate and start traveling.
2. What happens when the electrons reach the light bulb?
They seem to be absorbed by the light bulb and then power it
When electrons reach the light bulb they complete a circuit, causing the bulb to glow briefly.
, Activity A: Get the Gizmo ready:
Wavelength and ● Check that the Voltage is 0.0 volts and Potassium
flux is selected.
Introduction: Through the centuries, many scientists have debated whether light is a wave or a stream of tiny
particles. In the 1800s, most scientists agreed that phenomena such as refraction and diffraction supported the
“light as a wave” theory. However, Albert Einstein’s explanation of the photoelectric effect showed that light can
act like a stream of particles as well.
Question: What factors affect the ability of light to free electrons from a metal surface?
1. Observe: Click Flash the light with a variety of wavelength values. What do you notice?
The lower the wavelength, the faster the electrons travel
2. Observe: The photon flux is a measure of how bright the light is. It is equal to the number of photons that
are released in a given time. It is given as photons (γ) per millisecond (ms).
Click Flash the light with a variety of Photon flux values. What do you notice?
An electron is detached for every photon flux that it interacts with
3. Form hypothesis: Answer the following questions based on what you have observed so far.
A. Which factor determines how many photons will strike the metal? The photon flux
Explain: The photon flux is the number of photons that are released at a given time.
B. Which factor determines how much energy each photon has? Once the photon has
hit the electrons,
speed will vary on
the wavelength
Explain: The smaller the wavelength, the faster the electron/photon will travel. I
assume this is because it carries more energy.
4. Investigate: Set the Photon flux to 1 γ/ms. Use the Gizmo to find the longest wavelength that will dislodge
an electron from the metal surface. What is this wavelength?
530 nm
5. Predict: Set the Wavelength to 540 nm. What do you think will happen if you flash the light with a photon
flux of 1 γ/ms? What if you flash the light with a flux of 10 γ/ms?
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