me! Materials Needed: Desktop or Laptop Computer and flash enabled web browser Course Objectives: 1. Define and utilize ray properties of light and optics. Topic: Refraction and Lenses Activity 1 - Refraction and Snell's Law: To begin this week's lab, proceed to: https://phet.colorado.edu/sims/html/bending-light/latest/bending-light_en.html Once you have the browser open you will see something like the screenshot below: Figure #1 The screenshot shows a laser which is turned on, shining light from air to water. If you drag the protractor so that the central point is over the laser light when it hits the water, then you can measure the angles between the laser beam and the normal (dashed line) on both side of the water. 1. Please go ahead and measure the angle between the incoming light and the dashed line going up. Also, please measure the angle between the light in the water, and the dashed line going down. Write the answers below and comment on whether the angles SHOULD be the same, different, in what way. You may have already read in the textbook that Snell's Law states that light entering into a different substance, at some angle, will "refract" by some angle which is given by Snell's Law, n1*sin(1) = n2*sin(2)(eq. 1) 2. Check that Snell's Law is correct for the default situation in the simulator. Develop a method to check this, write it out below, and then proceed to test the theory. Write the results of your test below as well. Hopefully you found that Snell's Law does apply to the situation depicted in the simulator. Now let's use Snell's Law in a more practical way, to figure out what an unknown substance is made of!! 3. On the right side of the screen you are able to change the lower material to a different substance, Mystery A. Please do so and then develop a method to test the index of refraction of the substance Mystery A and write down your procedure below. You must take at least 5 sets of data with the protractor in your method! 4. Write out your data and your conclusions of your tests below. Include a guess as to what the mystery substance is! So great, light hits a different substance at some angle with respect to the normal and it bends. Big deal. It becomes a rather big deal when discussing people with imperfect vision and their desire to see correctly! The light that comes into the their eyes is not bending properly, because their eye has formed slightly differently than normal. The way to correct this slight deformity is with a pair of "prescription lenses"! In order to better understand eyeglasses, let's first do our best to understand thin lenses! Activity 2 - Color Vision To begin, proceed to the webpage: https://phet.colorado.edu/sims/html/color-vision/latest/color-vision_en.html Both light and pigments give us the rainbow of colors we see. Pigments are the chemicals which reflect the light that bounces on them and gives us colors we see. But what about the color of light itself? How does the color of the light affect what we see? Please follow the steps below to avoid confusion. Open Single Bulb screen. Click on the single bulb flashlight on the first screen. You should see this: The flashlight should not be on. What is the person seeing? (what they see is in the bubbles around their head) ________________________________________ Click on the red dot on the flashlight. What is the color of the light that is directed at the person's eyes? ___________________________________________ What color do they perceive? (in the bubbles around their head) ____________________________________________ 1. Drag the slider below the bulb color to the left or right. What do you notice about what is perceived? ______________________________________________________________________________________________________ 2. Click on the grey button and move it to the right to add filters. 3. Click and drag the slider below the filter color spectrum. What do you notice about the light that is perceived? _____________________________________________________________________________________________________ 4. What does the filter do? ___________________________________________________________________________________________________ 5. Click on the white light bulb (the one on the left) and move the slider for the filter color. What do you notice? _________________________________________________________________________________________________ 6. Why do you suppose this happens? ___________________________________________________________________________________________________ 7. Click on the light beam on the right, move the filter slider, and make some observations about what you notice about the light, the filter, and what is perceived. ___________________________________________________________________________________________________ 8. What did the filter do to the light? __________________________________________________________________________________________________ Part 2 1. Click on the reset button: Then click on the RGB bulbs button: 2. No lights are on. What color is perceived? _________________________________________ 3. Click on the Pause/Play button: 4. Click on the sliders and add light by sliding up all the way. Fill out the data table below with your observations: Light Color Perceived Color Just red Just green Just blue Red and green Red and blue Green and blue Red, green, and blue 5. If you don't move the sliders all the way up, how does it change what you perceive? ________________________________________________________________________________________________________ 6. Summarize what you have learned from this investigation. __________________________________________________________________