CH.2 LIGHT AS A WAVE

CH.2 LIGHT AS A WAVE

LW: 2.4.1 WARM-UP Students observe which types of light from the sun reach Earth s surface. (5 min) Light that Reaches Earth's Surface Earth s atmosphere can absorb some wavelengths of light emitted from the sun. This diagram shows which types of light are absorbed in the atmosphere, and which types of light travel through the atmosphere and reach Earth s surface. Use this diagram to help you think about which types of light could be causing the damage that can lead to skin cancer.

LW: 2.4.1 WARM-UP From the types of light that reach Earth s surface, which do you think could be causing skin cancer? Explain your reasoning.

LW: 2.4.2 HANDS ON Students test different types of light on genetic material in the Light Waves Simulation, then model their results. (30 min) Investigation Question: What makes types of light different? The sun gives off many types of light, but it is still unclear why one or more of these types can cause skin cancer and the others cannot. What makes these types of light different?

LW: 2.4.2 HANDS ON Investigation Question: What makes types of light different? Share ideas about which types of light may cause skin cancer with a partner. Remember that gamma rays and X-rays are absorbed by the atmosphere.

LW: 2.4.2 HANDS ON Investigation Question: What makes types of light different? You will use the Light Waves Simulation to individually test how each type of light from the sun that reaches Earth s surface changes genetic material. You will then use the Modeling Tool: Light s Effect on Genetic Material to model your results.

Notice the types of light feature. The last time you made a model you chose a light source, noted the change it caused, and traced energy. For this model, you will also choose a type of light and write it in a box, and then draw an arrow to connect it to a change box, writing the change that type of light causes. Use Model A (on the first page) to show how different types of light change genetic material. You will use the word bank on the right to complete your models. LW: 2.4.2 HANDS ON Project Modeling Tool: Light s Effect on Genetic Material (Model A)

You will use Model B (on the second page) to show types of light that cause no change to genetic material. LW: 2.4.2 HANDS ON Project Modeling Tool: Light s Effect on Genetic Material (Model B).

LW: 2.4.2 HANDS ON You will be testing each type of light individually (ultraviolet, any color of visible light, infrared, microwave, and radio). You will be shining each of these types of light on genetic material and inspecting its effects. By looking for a change, you can determine if the energy from that type of light was absorbed by the material.

LW: 2.4.2 HANDS ON

LW: 2.4.2 HANDS ON Use the Light Waves Simulation. Make sure to change the light source to LASER and move the slider back and forth to change the type of light. USE THE SIMULATION TO CHANGE THE LASER LIGHT Complete Modeling Tool A and B

LW: 2.4.2 HANDS ON Summarizing Results After you have tested the five types of light from the sun that reach Earth s surface, answer these questions by choosing one or more options.

LW: 2.4.2 HANDS ON Let s share what you discovered. 1. Did energy from all types of light get absorbed by the genetic material in skin cells? No, visible light, microwaves, and radio waves were not absorbed. 2. How could you tell if the energy was absorbed? There was a change to the genetic material; You could see that the light beam stopped at the material; You could see that the energy went into the material. 3. Based on these results, which type or types of light are most likely to be the cause of skin cancer? Ultraviolet (UV)

LW: 2.4.2 HANDS ON Let s Focus on infrared light. Can infrared light cause damage that leads to skin cancer No, because it causes increased kinetic energy, not damage. When infrared light hits molecules in our skin, the kinetic energy of the molecules increases and we feel this as warmth. Infrared light can make skin feel hot, but this feeling is not the same as the damage that can lead to skin cancer.

This key concept provides another way of thinking about the Investigation Question: What makes types of light different? LW: 2.4.2 HANDS ON Different types of light have different wavelengths. This determines whether they are absorbed by a material, and what kind of changes they can cause if they are absorbed.

LW 2.4.3 DISCUSSION Students use evidence to make an argument about whether or not a light bulb can cause skin cancer. (10 min) Now that you have investigated the effect that different types of light have on the genetic material in skin cells, you will apply what you have learned to consider the question, Can a light bulb cause skin cancer? Consider these two claims: 1. Claim 1: Light from the sun and light from a light bulb can cause skin cancer. 2. Claim 2: Light from the sun can cause skin cancer, but light from a light bulb cannot. Use this evidence to decide which claim they agree with, as well as their completed Modeling Tools from Activity 2

Consider these two claims: 1. Claim 1: Light from the sun and light from a light bulb can cause skin cancer. 2. Claim 2: Light from the sun can cause skin cancer, but light from a light bulb cannot. LW 2.4.3 DISCUSSION Think on your own for a few minutes about which claim you agree with. Consider the evidence in relation to the claims. BE PREPARED TO SHARE Present your argument to a partner. You can use the language from our Scientific Argumentation material to help explain your thinking. Use this evidence to decide which claim they agree with, as well as their completed Modeling Tools from Activity 2 Answer Questions on screens after you have described the evidence to support your thinking.

LW 2.4.3 DISCUSSION Answer Questions on screens after you have described the evidence to support your thinking.

LW 2.4.4 HOMEWORK You will read an article titled What Is Melanin? about a substance found in skin cells. Melanin is a substance found in almost everyone s skin. The article will help you understand what happens to light when it hits the melanin in skin cells. In the next lesson, we will be learning more about how melanin might affect the skin cancer rate in Australia. Read and annotate the article What is Melanin using the Active Reading strategies Then, answer the questions below the article. Learning more about melanin, might help you solve the mystery of Australia s high skin cancer rate.