60 minute physics. Light. Nine hands-on activities: with GCSE Physics curriculum links. Light. Electric circuits. Machines & electromagnets

Transcription

1 60 minute physics Nine hands-on activities: with GCSE Physics curriculum links Mapping data Digital Electric circuits Machines & electromagnets Flight & movement Storing energy Forces & motion Changing states

2 STEM engagement materials developed for the Royal Air Force This activity forms part of a suite of physics-related activities developed by West Yorkshire STEM in collaboration with the University of Leeds. They have been funded by the Royal Air Force to encourage pupils to think positively about STEM generally and physics in particular. Each activity has been designed to be interactive and linked to GCSE physics specifications of OCR and AQA. Stretch or extension activities are provided in the content for additional follow-up beyond the session. To run this activity you will need: Computer with internet facilities for groups or teams of pupils (around 4 per group). Powerpoint facilities to introduce the content and activities (using.pptx ). (for activities / to produce colours) Notepad should be available on each computer. Copies of Playing_with_light_student_activity.pdf handout for each group/pupil. 1 Certificate of completion for each student - produced as part of these materials (Certificate_light.pdf). Level: KS3/KS4 GCSE science curriculum links: nature of light, electromagnetic spectrum, primary colours Objectives of the session Understand visible light and how it forms part of the electromagnetic spectrum. Understand the different types of electromagnetic radiation. Understand the properties of primary colours and how they can be used to create colour. Session length: 60 mins Session overview Visible light (15 mins) Magnifying images (15 mins) Mixing primary colours to create colour (30 mins) Extension: Make a spectroscope to analyse light Turn an old CD into a spectroscope to analyse light. (Available at: 2

3 Slide 1 Introduction to the session Introduce yourself as the facilitator and outline (briefly) your STEM background. Ask STEM Ambassadors (if present) to (briefly) introduce themselves and to say which STEM discipline/ industry they are from. Slide 2 What is light? The word light refers to the electromagnetic radiation that we can detect with our eyes i.e. the visible part of the Electromagnetic Spectrum (EM). All waves in the EM can travel through a vacuum and travel at the speed of light (very different to other types of wave like sound, which is much slower and cannot be transferred through a vacuum). In order to better understand light we need to look more closely at the EM. Slide 3 The electromagnetic spectrum We identify an electromagnetic wave by measuring its frequency, amplitude and wavelength. The different descriptions of EM radiation in the EM spectrum are determined by their use. As you can see EM waves with a certain function are determined by the range of frequencies they encompass. 3

4 Slide 4 Amplitude and wavelength Frequency: the number of times something passes a certain point; in the case of EM radiation measured in cycles per second or Hertz (Hz). Wavelength is the distance from a point on a wave to the corresponding point on the next wave. Amplitude is the measurement between the peak or trough of a wave and the mid-point between the two. Variations in amplitude reflect variation in the power or intensity of a wave; high amplitude high intensity low amplitude low intensity. Slide 5 Electromagnetic radiation types In order to remember what order the different types of EM radiation fit on the scale students use the following rhyme Lets think of some examples that use different types of radiation waves... Slide 6 Match the wave length to its use Lets have a go at Activity one: match the wave length to its use (on your handout). Mobile phone = radio waves. Radiotherapy machine = Gamma rays. Sunbed = Ultraviolet waves. TV remote = Infrared waves. Thermal imaging camera = infrared waves. 4

5 Slide 7 Mirrors In order to produce detailed images from the light that falls on them we might need to magnify them. Magnification (from a lens or mirror) is expressed as magnification = image height / object height. Question = 40cm/8cm = magnification 5x. Slide 8 Visible light Visible light occurs in the nm wavelength range with frequencies between 750 and 380 THz (that s very short wavelength and very high frequency). Each colour occupies a certain portion of the spectrum before fading into the next colour. Red occupies the relatively longer wavelengths and lower frequencies and violets the relatively shorter wavelengths and higher frequencies. Slide 9 Questions! Which of the following frequencies and wavelengths do you think we could see and what colour would they be? a. 550 THz & 550 nm (Green) b. 480 THz & 630 nm (Orange) c. 610 THz & 490 nm ( Blue) d. 760 THz & 390 nm Not visible) 5

6 Slide 10 Producing colour Back in the olden times computer monitors looked like this. We called them CRT monitors. CRT stands for Cathode Ray Tube. The reason for this was the way that the picture on the monitor had to be created. The CRT was essentially an electron gun that shot a beam at dots (which lit up when hit) printed on the inside of the monitor s glass screen. The beam scanned across the dots rapidly, switching on and off in order to create a picture. Once the cycle of scanning was complete the beam would return to the start and project another picture on the screen. Because this happened so quickly the pictures appeared to be moving. Slide 11 Producing colour (continued) Consequently the picture quality wasn t very good and the equipment was bulky and expensive. Modern Liquid Crystal Display (LCD) flat screen monitors still use dots behind a screen and these are still clustered in RGB dots but they are now much smaller and activated directly by electrical current. Modern high quality displays like Apple s Retina give very high resolution images. Slide 12 Practice making colour on a webpage A great way to practice mixing RGB light to make colours is to modify the background colour on a web page. The code that you enter directly controls the amount and intensity of either red, green or blue light on the entire page as a background colour. You can also adjust the font colour for written text in the same way. On an ordinary PC open Notepad or other similar text editor (tip find notepad in Accessories on Microsoft Office). Save the file as a.txt file and then save a copy of the file but instead of.txt use.html (you will have to manually type this in as it is not an option on the drop down menu). 6

7 Slide 13 Practice making colour on a webpage Now open the.html version of your file (it should open in your default browser e.g. Explorer). You should see something like this. You might find it useful to look at the information for Activity two on your handouts - there s lots of useful tips! Slide 14 Editing colours You can edit your text in Notepad, save your changes and then view the updated website at your leisure but the part we are interested in is the background colour. This is controlled by the <body bgcolor= #FFFFFF > tag. The capital Fs control the hue and intensity (wavelength and amplitude) of light for the Red, Green and Blue dots on the monitor. We use a combination of numbers (0 9) and letters (A F) to give a maximum of 16 different wavelengths and amplitudes for each of the primary colours. Have a look at the table below to try out the different combinations for the three primary colours then have a try at figuring out the mixing for others (Activity three on your handout). As you will have now found, all colours in the visible spectrum can be created by controlling the wavelength of light emitted from three primary colour sources. When we see certain colours e.g. the yellow skin of a banana or the blue sky that means that the object reflects that wavelength (or wavelengths in that band) and our eyes pick this up and our brain makes sense of it. Remember visible light is only a very small part of the EM spectrum and there are lots of other energy beams that we can t detect without special equipment. Slide 15 RAF examples: infrared in action! Infrared light is crucial for the RAF! Night-vision equipment allows pilots to see in the dark. It also allows the identification of materials that give off heat as shown in the aircraft example here. 7