The Eye & the Camera (Oxford AQA IGCSE Physics)
Revision Note
The Eye & The Camera
In your exam, you may be asked to compare the function of the human eye and a charge-coupled device (CCD) camera
A CCD camera (digital camera) uses a convex lens that focuses light onto a screen to form an image
The image can be viewed on the camera screen or transferred to a computer and printed
An older model of camera uses a convex lens to focus light onto a photographic plate in the back of the machine this is called a photographic film camera
The film can be "developed" using chemicals in a dark room and the photos formed on the film
A CCD camera
A photographic film camera
Comparing The Eye and The Camera
The Eye | The Camera | |
|---|---|---|
Image formed | Real, inverted and diminished (magnification < 1) | |
Lens type | Variable focus converging lens | Fixed focus converging lens |
Focussing adjustment | The ciliary muscles contract and relax changing the thickness of the lens | The lens on the front of the camera can be adjusted to move closer or farther away from the object |
Image detection | Light-sensitive cells on the retina detect the light from an image | Sensors in a CCD (digital) camera or the photographic plate in a film camera |
Brightness control | The iris controls the diameter of the pupil | The aperture is the hole in the centre of the lens that allows light to pass into the camera. It contains rotating blades that open to let light in when you press the shutter |
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