Gizmo - Radiation Answer Key

Gizmo - Radiation Gizmo Warm-up In the Radiation Gizmo, you can focus the light of a super-powerful flashlight upon a kernel of popcorn and see what happens. The lens, which focuses the light, can be moved to the left or right. The Temperature slider controls the heat of the metal filament inside the light. Scientists use the Kelvin scale to measure the temperature of very hot objects. It is like the Celsius scale except 0 K (absolute zero) is the coldest anything can ever be.   Slowly move the Temperature slider all the way to the right. What happens? It makes the light yellow and takes 2.7s to pop the popcorn without the lens.   The light energy emitted by the flashlight is called radiation. Slide the lens so the distance to the flashlight is 40 cm. Press Play (). What happens? It popped even faster at 1.25 now.   Do you think the kernel will pop if you place cardboard in front of the flashlight? no Click Reset (). At the top of the Gizmo, next to Obstacle, select Cardboard. Press Play. What happens? The light got a little darker and it does not do anything because there is cardboard in front. Activity A: Get the Gizmo ready: What causes the • Click Reset. popping? • Set Temperature to 1500 K. • Slide the lens so it is 50 cm from the light. • For Obstacle, select None. Question: How does heat get from the flashlight’s metal filament to the kernel?   Observe: Press Play. How long does it take the kernel to pop? 67.3 sec   Form hypothesis: Inside the light bulb is a very hot piece of metal, called the filament. It gives off light because it is so hot. In addition, the glass bulb gets hot and heats the air. How do you think heat gets from the filament to the kernel? If electricity flows through the filament, then maybe it travels though radiation or waves! light   Predict: Click Reset and select Cardboard. This blocks all light and some of the hot air. Based on your hypothesis, how will this affect popping time? Explain. I think it will not pop or take a LOT of time to pop, this might be either because the cardboard absorbs the light and heat or because it reflects it away.   Test: Click Play or Fast forward (>>). Was your prediction correct? yes Predict: Click Reset and select Red Glass. This lets most of the light through but still blocks some air. What do you think will happen? Explain. I think it might take some time but will pop in the end.   Test: Click Play or Fast forward. What did you find? I found that I was correct it took about a minute but in the end it did pop. Draw conclusions: When the popcorn kernel popped, was it because it was heated by light (radiation) or hot air from the flashlight? Explain how you know this. It was heated by light (radiation) this is because any kind of electromagnetic radiation will work to the effect that it absorbs it.   Activity B: Get the Gizmo ready: Out of sight • Click Reset. • Slide the lens so it is 60 cm from the light. • Set the Temperature to 2000 K. Goal: Understand that light is both visible and invisible.   Observe: Select Blue glass. How does this affect the light that gets to the corn? The light is blue/violet and makes the corn pop faster because that is the power of ultra-violet rays.   Conjecture: Will the corn pop when you start the simulation? Explain. yes because the violet-rays can be stronger than normal. Experiment: Click Fast forward. What happens? The corn pops very fast and as I predicted it popped faster. Draw conclusions: The filament radiates both visible light (orange in this case) and invisible light (infrared light). Did the blue glass block infrared light? Explain how you can tell. The blue light might have blocked the infrared light because after the blue because it turned blue not orange.   Run Gizmo: Click Reset. Remove the glass. Click Play. When does the corn pop? 2.2 sec Analyze: Compare the popping times with and without the blue glass. Is most of the radiation given off by the filament red or infrared? Explain. It took 2.7s for both to pop so the same amount of energy is given from both.   Test: Click Reset. Select Cardboard and then click Fast forward. Does the cardboard block infrared light? Explain. yes because after placing the cardboard the kornut does not pop.   Extend: Do you think the blue glass or the cardboard gets hotter in this experiment? Why? Card board because the cardboard is not letting the light go through and the blue glass does. Activity C: Get the Gizmo ready: Blended light • Click Reset. • Set the Temperature to 1300 K. Question: How does temperature affect the kinds of visible light produced? Observe: Colored glass allows some light through and absorbs (or reflects) the rest. A. Does green glass let red light through? yes B. Select Red glass. Does red glass let red light through? yes   Analyze: Select Blue glass. Slowly increase the Temperature to 3600 K. What happens? What happens is that the color changes from intense red to yellow.   Draw conclusions: The radiation given off by the flashlight filament is a mixture of colors. Does it give off more blue light at 3600 K or 1300 K? Explain. It gives off more blue light at 3600K because that temp is hotter and the rays are stronger.   Observe: Set the Temperature to 2500 K. Observe the light through the different glasses. A. The orange light radiated at 2500 K is a blend of which colors? Explain. It is a mix of red and yellow because it may be the average temp. B. Is there more red light or green light? How do you know? Red light because the light from the starting point is intense and visually noticeable. Compare: Select Red glass. Slowly slide the Temperature slider to 1000 K. Does the orange light at 2500 K have more or less red light in it than the red light at 1000 K? Explain. Less red light than the red light at 1000K because the red light is more intense at the beggining.   Challenge: Purple glass lets red and blue light through but not green. What would you see as you increase the temperature from 1000 K to 3600 K using purple glass? you'd see a purple color that gets brighter as the temp. Increases the purple light lets through red and blue which both increase with temp. since green is blocked you'd see a lighty purplish color.