Science and Data Acquisition Creative Learning Systems www

Science and Data Acquisition © Creative Learning Systems www. creativelearningsystems. com

What You’ll Learn… § The safety rules for using lasers § How to measure and compare the output power of your laser to other light sources § Characteristics of laser light waves and how wave interference can create laser light patterns. Stuff You’ll Need… § LASER and its power adaptor § Photometer/receiver (speaker) with power adaptor and a stand to mount the detector on © Creative Learning Systems www. creativelearningsystems. com

What You Should Know… § It is very important that you know and follow all the LASER safety rules to prevent injury § How to handle the LASER equipment carefully to prevent accidental damage to the equipment § How to properly store the LASER communication equipment when you are finished for the day © Creative Learning Systems www. creativelearningsystems. com

What You Should Know… § Laser safety is the avoidance of laser accidents, especially those involving eye injuries. Since even relatively small amounts of laser light can lead to permanent eye injuries, lasers are subject to official regulations and they are classified. § Lasers have been classified by wavelength and maximum output power into four classes and a few subclasses since the early 1970 s. The classifications categorize lasers according to their ability to produce damage in exposed people, from class 1 (no hazard during normal use) to class 4 (severe hazard for eyes and skin). § There are two classification systems, the "old system" used before 2002, and the "revised system" being phased in since 2002. © Creative Learning Systems www. creativelearningsystems. com

What You Should Know… These are the parts that make up your Smart. Lab Laser Collection Stand Photometer Receiver Light Bulb w/ Stand Missing Something? Then you won’t need it yet! Magnifying Glass The Diode LASER Power Adapters (2) © Creative Learning Systems www. creativelearningsystems. com

Do It! Examine the LASER This is the laser you will be using for all your laser communication experiments. Study the photos below to see how you connect the laser. Audio Cable (You don’t need this yet) ON - OFF 635 nm Diode Power Adaptor Laser Side View Shim for adjustment Laser Back View © Creative Learning Systems www. creativelearningsystems. com

Do It! Examine the LASER What kind of laser do you have? Read the yellow label on the side of your laser. Is it the same as the label you see here? You can learn three things by reading your label. It tells you the laser type, its maximum power output, and the classification of your laser. Read your Label 635 NM Diode Laser Side View © Creative Learning Systems www. creativelearningsystems. com

Do It! Examine the LASER Your laser has a copper shutter to block the path of the laser beam as an added safety feature to prevent accidental shining of the beam even when the laser is on. Open the shutter when you are ready to send the beam. Close the shutter when you want to block the beam. 635 NM Diode Beam Shutter Lever Beam is Blocked Laser Front View Shutter Closed View Beam is NOT Blocked Shutter Open View © Creative Learning Systems www. creativelearningsystems. com

Do It! Measure Laser Power Now that you know a little more about laser safety and classification systems, you might be wondering how powerful your laser is. You can find out by setting up and doing this experiment. The photometer measures the intensity of the light that is hitting the detector sensor. Power Adaptor Detector on a Stand Photometer/Receiver (speaker) 1. 5 meters. 890 LASER Power Adaptor © Creative Learning Systems www. creativelearningsystems. com

Do It! Measure Laser Power 1 Aim your laser beam on the detector sensor 3 Write this number on your Caution Sign 2 Set the dial to 2 m. W (2 milliwatt) © Creative Learning Systems www. creativelearningsystems. com

Do It! Create Laser Safety Sign in Word Document Create a Laser Sign in your Word Document. Make sure it looks similar to this one! Be sure to incorporate all of the important information! Use your label and your power reading

Do It! Measure Other Light Sources 1. You will be using the Photometer/Receiver unit and adapter for the first part of this procedure. 2. In this procedure you will determine the different types of light sources you would like to measure. Set the selector switch to 20 m. W. 3. Measure at least three (3) different light sources (examples: Classroom lights, flashlight, overhead projector, sun). Organize this information in your Word document. 4. Note that the readout increases as the detector is held closer to the light source. As the detector gets further away the readout decreases. An excellent way to demonstrate this is with a flashlight. Hold the flashlight right up against the detector. As you draw the flashlight away from the detector the reading decreases. If this happens tip the detector away from the sun slightly until you get a reading under 20 m. W. Detector on a Stand © Creative Learning Systems www. creativelearningsystems. com

Do It! Laser Speckle Patterns Use the frosted or “soft white” incandescent light bulb for this experiment. Place the light bulb in something to hold it stationary (a cup, a cone of clay or something) and aim the laser beam into the center of the bulb. Note: Not everyone will see the same thing. Ask everyone to be perfectly honest in sharing what they see in the bulb. Research: View the light bulb from an angle (be careful NOT to look straight in line with the laser beam). Describe what you see in your Word Document. Ask two different classmates to try it and describe what they see. Power Adaptor LASER Lid off a can of spray paint

Do It! Laser Speckle Patterns Most people will see a cloud of bright red sparkling specks floating in the glowing red bulb. Move your head side-to-side and then up and down. What happens to the red dots when you do that? Ask some classmates to try it and describe what they see. Describe what they see in your Word Document. Why do you see red dots? Do you think that the light bulb is shattering the laser beam into thousands of little tiny pieces inside the bulb? Power Adaptor LASER © Creative Learning Systems www. creativelearningsystems. com

Do It! Laser Speckle Patterns Use the magnifying glass to try to enlarge your laser beam as you project it on the wall. Look closely at the red dot area on the wall to see if you detect laser speckle. It won’t be quite as dramatic as the light bulb method, but it still works pretty well. SAFETY TIP: Keep your back towards the laser while you are looking at the dot patterns Research: Describe what you see in your Word Document. Power Adaptor LASER © Creative Learning Systems www. creativelearningsystems. com

Do It! Laser Speckle Patterns What you are seeing is known as laser speckle. Laser light is different from ordinary light in two ways: It is mono-chromatic (one color) and coherent. Coherent means that all the peaks and troughs of the light wave line up over very long distances. When laser light scatters off of surfaces, these peaks and troughs can interfere with each other to produce bright and dark spots. If the surface is regular, one sees a diffraction pattern. If the surface is random and diffuse, one sees laser speckle. Incoherent Light Waves You can learn more about laser speckle online. Try your favorite search engine and see what you can find. Coherent Light Waves © Creative Learning Systems www. creativelearningsystems. com

Do It! Laser Speckle Patterns SAFETY TIP: Keep your back towards the laser while you are looking at the dot patterns Try this experiment, but remember to never look directly back into the laser beam. Fold a white piece of paper like an accordion. See if the irregularity of this surface changes the speckle pattern. Try catching the beam with a flat piece of paper in your hand. Try holding the paper in your hand rotate it to different angles to make the beam even wider. Do you still see a speckle pattern? Try this with flat paper and the folded paper. Record your observations in your Word Document. Power Adaptor LASER © Creative Learning Systems www. creativelearningsystems. com

Do It! Laser Speckle Patterns Have you noticed how the dot patterns seem to hover above the surface of the paper, and they have kind of a 3 D dome shape like tiny jelly particles floating over the paper. Try closing one eye to see how that changes the image you see. Switch eyes and move your head sideto-side. What changes did you observe? You will still see the speckles, but are they 2 D or 3 D when you have one eye closed? Record your observations in your Word Document. I can still see the speckles, but they are different. Dots hover in a dome shape Power Adaptor Side View LASER © Creative Learning Systems www. creativelearningsystems. com

Do It! Laser Speckle Patterns When you switched from two eyes to one eye it effected your ability to see things in three dimensions (3 D). You need both eyes to enable your brain to compose a 3 D image and give you depth perception. If you are having trouble seeing 3 D, this might mean that you might have problems with your binocular (two-eyed) vision or stereo vision (3 D vision). © Creative Learning Systems www. creativelearningsystems. com

Questions/Research 1. 2. 3. 4. 5. Formulate a Laser safety sign. Define MASER Define LASER Describe the difference between a MASER and a LASER. Your team’s observations and two other people’s observations from the light bulb and folded paper experiments. 6. Which light source had the highest m. W? Lowest? 7. A laser has which type of light waves (coherent or incoherent)? 8. Describe the differences between coherent light waves and incoherent light waves. © Creative Learning Systems www. creativelearningsystems. com

Before moving on to Part 2 Mr. Ochs needs to check your work before moving on to part 2! © Creative Learning Systems www. creativelearningsystems. com