Detecting light

Cameras and our eyes detect light. In each case, they have:

  • a material that is sensitive to light
  • a change that happens when this material absorbs light

The camera

Cameras are devices that focus light from an object onto a photo-sensitive material using a lens. In an old-fashioned camera, the photo-sensitive material was camera film. When the film absorbed light, a chemical change produced an image in the film, called the ‘negative’. This was used to produce a photograph on photo-sensitive paper.

In a modern camera or the camera in a mobile phone, the photo-sensitive material produces electrical impulses, which are used to produce an image file. This can be viewed on the screen, or its information sent to a printer.

A cross-section of a camera showing the converging lens, aperture, shutter and focus point.A cross-section of a camera

The eye

Like the camera, the eye focuses light from an object onto a photo-sensitive material. However, in the eye, this material is the retina. The retina contains cells that are sensitive to light. They produce electrical impulses when they absorb light. These impulses are passed along the optic nerve to the brain, which interprets them as vision.

The retina contains cells that are light-sensitive and produce electrical impulses when they absorb light. The impulses are passed along the optic nerve to the brain, which interprets them as vision.Light is focused onto the retina of the eyeStructure of the eye, showing the iris, pupl, lens, retina and optic nerve.Component parts of the eye
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