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Photoelectric Effect

Light acts like both a particle and a wave.

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How do digital cameras take pictures?

Credit: Capt Kodak
Source: http://www.flickr.com/photos/35114754@N00/271901646/in/photolist-q2yTq-q2FEd-q6QBC-vyd6X-AvSwG-AvSwP-AvSwT-Aw4sa-Aw4sc-C5oLJ-DjJoA-NvimY-PzPRL-PApmZ-2bbnY1-3KAqPi-4qakQU-4xq7Uc-4xq7Zn-4xuED9-4xuEKs-4xBSjP-4xBSpk-4D9z8h-4FC5bW-4GjbSh-51M3CH-559ZhQ-5cSwzS-5g4QHz-5g4QXc-5rsj5P-5rwDgu-5x6yGR-5x6yMV-5x6yPp-5zfhJg-5zjxJw-5BFP9U-5JD1cX-5JHgEs-5SqiXn-66RCwu-6r3BTe-6rvdtk-6HDsWj-6KE7CM-71ghyc-74ty7S-bkdJog-8vvbPZ
License: CC BY-NC 3.0


Zoom!  Focus!  Snap!  You’ve just taken a gorgeous picture that saves to your digital’s camera memory.  But what is the process that allows you to capture memories?  How does the camera both take the picture digitally and then save it?  Charged-Coupled Devices (CCD) like digital cameras and image sensors use the photoelectric effect to produce the digital images you see on the internet, the smart phone, and the camera.  Digital cameras have a grid of metal pixels that lay on a silicon wafer called a CCD chip, and when light touches the pixels, it gives its energy to the electron and the electron is kicked off.  The electron’s movement can be seen as a change in charge or an electric current.  What the camera saves is the change in charge for each pixel, and this data is the digital image we see on the camera. 

Creative Applications

  1. The human eye works in a very similar way.  It has rods for scotopic vision and cones to detect color.  Which part of the camera is most similar to the rods and cones? (CCD wafer).
  2. Why would camera manufacturers want there to be as many pixels as possible?
  3. How can manufacturers increase the number of pixels?






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