Imaging Partnership STEM TEACHER RESOURCES

Transcription

1 Imaging Partnership STEM TEACHER RESOURCES

2 Light We Can t See LESSON TWO

3 What you will learn: That light is made up of different colours and that those colours have different temperatures. That our eyes neutralise light but that cameras see it as it really is. That the colour of light, through White Balance, can be manipulated in camera or through software. That invisible light is made up of different types of rays. The importance of being able to see through objects (non-invasive). Potential careers using invisible light.

4 What you should be able to do: Take photographs under a range of lighting conditions and compare results. Demonstrate ability to manipulate white balance for realism/emotion in camera. Record different types of invisible light and their uses. Review potential careers using invisible light. Take photograph using correct techniques as required.

5 Herschel s Experiment a reminder Recommended video:

6 Herschel Experiment In 1800, Frederick William Herschel discovered that: Each colour of the spectrum has a different temperature* Light exists outside the visible spectrum The highest temperatures are in the range outside visible light

7 White Balance 1 Most of us have taken photographs indoors that have turned out unexpectedly to be bright orange. Have you ever wondered why? Well, some artificial lighting casts a warm (orange) glow and some casts a cool (blue) glow.

8 White Balance 2 Our cameras see the colour of light as it really is, but those colour casts can be really annoying. Most now have a feature called Auto White Balance which reads the temperature of the light and adjusts it automatically.

9 White Balance 3 If you go to the White Balance setting on your camera, you will see a range of other choices, not just Auto Usually, these will be Daylight Cloudy and Shade for natural light. As you go through these settings, the images will become warmer (more orange) each time. We can use these settings to make our images warmer or cooler. Try taking a range of photographs under different lighting and with different WB settings.

10 Filters You can also affect the colour cast in your images by placing coloured transparencies over the lens when you are capturing images. Try it and see what happens!

11 Invisible Light As we saw in Herschel s Experiment, most light is invisible This includes: Infrared, which was shown to be warmer than red light Ultraviolet, which was cooler than violet light As well as Gamma and X-rays So the question is, if we can t see it, then why is invisible light important? Let s look at each one in turn.

12 Infrared 1 Infrared radiation is used in industrial, scientific, and medical applications. Night-vision devices using infrared allow people or animals to be observed without the observer being detected.

13 Infrared 2 Thermal-infrared imaging is used for both military and civilian purposes and works by creating images based on differences in surface temperature from objects and their surrounding environment

14 Infrared 3 Most cameras will only allow visible light and block out infrared by means of a filter. In infrared photography, those filters are removed to capture the infrared spectrum and another filter is fitted to block out visible light

15 Ultraviolet Ultraviolet is present in sunlight It produces vitamin D, which has health benefits It is what causes our skin to tan and ultraviolet lights are used in tanning salons However, overexposure can be dangerous and cause skin problems and cancers It s most common uses are for checking banknotes and for reading holograms on credit cards It s also used by police to look for evidence of bodily fluids

16 X-rays X-rays are most commonly used in healthcare Bones, being mostly made from calcium, absorb X-rays easily and show up as light images Too much exposure can be dangerous, which is why the dentist leaves the room when images are taken of your teeth Other uses include airport security, to check your luggage and in industry to check parts and produce 3D images of components (CT scan)

17 Gamma Rays Gamma rays are similar to X-rays, but are more dangerous to health They are used in similar ways, for example, in collecting images of horses legs, where a more detailed view is needed than an x-ray They are used to irradiate foodstuffs to kill off bacteria that would cause food to decay more quickly They are used at ports to scan containers

18 Invisible Light - Summary Overall then, what does invisible light help us to do? While there are a wide range of uses, by far the most important are that they enable us to see inside things, both bodies and parts such as engines We can do that without having to cut into them, or take them apart This can be done more quickly, so saves time It also saves money there is no recovery time so people don t have to be kept in hospital. Engines don t have to be put back together

19 Radiographer

20 So what have we learned today? Well, we looked again at Herschel s Experiment, to remind us that there is visible and invisible light. Also that light has different colours and those colours have different temperatures We learned that cameras see light differently to us and that we can adjust our images to make them warmer or cooler We learned about the different types of invisible light and how they can be used We also learned about different careers working in the area of invisible light