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Telescopes

Investigating converging lenses

Converging lenses are often used to produce images that are magnified. The amount of magnification depends on:

  • how curved the surface of the lens is
  • how close the lenses are placed.

There are two types of image that can be seen. A real image is the image formed where the light rays are focussed. A virtual image is one from which the light rays appear to come but don’t actually come from that image like in a mirror.

Converging lenses can be investigated by changing the distance between the object and the lens. Using the apparatus below, the object can be moved closer or further away from the lens. This is done in focal lengths – F, 2F and so on. The image can also be measured in focal lengths.

Converging lens

Investigating a converging lens

The results

More than two focal lengths:

converging lens 1a

image inverted, made smaller, appears between 1 and 2 focal lengths, real image produced

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