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Cards In This Set
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14.1.1 Solve problems involving the conversion between binary numbers and decimal numbers
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Binary numbers use base 2, while the decimal numbers we use everyday use base 10
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14.1.2 Describe different means of storage of information in both analogue and digital forms
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Analogue information can have an infinite number of values, but digital information is either one of two options (off/on, red/green)
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14.1.3 Explain how interference of light is used to recover information stored on a CD
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The information is encoded onto the surface of the aluminum through a series of bumps and flats, representing binary numbers 0 and 1 respectively
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14.1.4 Calculate an appropriate depth for a pit from the wavelength of the laser light
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Distance (d) = wavelength (λ) ÷ 4
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14.1.6 Discuss the advantage of the storage of information in digital rather than analogue form
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- Quality and corruption- Reproducibility (accuracy)- Portability and High Capacity- Manipulation
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14.1.7 Discuss the implications for society of ever-increasing capability of data storage
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- Moral and ethical implications of the collection of personal data by the Government- Effect on the environment- Loss of privacy
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14.2.1 Define capacitance
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Capacitance is the amount of charge that can be stored per unit potential of the sphere
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14.2.2 Describe the structure of a charge-coupled device (CCD)
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A charge-coupled device is a type of complimentary metal oxide superconductor (CMOS). An electric potential difference is generated by light liberating electrons from the valence band of a semiconductor.
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14.2.3 Explain how incident light causes charge to build up within a pixel
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Pixel - Regions within the silver dioxide containing three electrodes and acts as a capacitor
When light is focused on to the surface of the CCD, electron-hole pairs are produced in each pixel. Each photon of the incident light will produce one electron-hole pair such that the number of pairs produced will be proportional to the intensity of the light incident on the pixel. The electron pairs will migrate to the relevant electrodes resulting in a change in potential across the pixel. |
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14.2.4 Outline how the image on a CCD is digitized
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The resulting change in potential caused by the electron pairs migrating to the relevant electrodes is converted into a digital signal.
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14.2.5 Define quantum efficiency of a pixel
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The percentage of photons in the incident light that produce electron-hole pairs.
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14.2.6 Define magnification
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The ratio of the length of image on CCD to the length of the object
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14.2.7 State that two points on an object may be just resolved on a CCD if the images of the points are at least two pixels apart
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Two points on an object may just be resolved on a CCD if the images of the points are at least two pixel apart
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14.2.8 Discuss the effects of quantum efficiency, magnification and resolution on the quality of the processed image
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The magnification of a given object, the greater the length of the image on the CCD, and the greater the number of pixels, meaning the image will be more detailed
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14.2.9 Describe a range of practical uses of a CCD and list some advantages compared with the use of film
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Used in...- imaging devices such as photocopiers, fax machines, mail sorters and bar code readers- closed circuit television cameras and video cameras- astronomy (to detect faint/distant objects)- detecting low levels of radiation- testing the effectiveness of drugs binding to their target- X-ray imaging
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