SS2 Third Term Physics Lesson Note – Application of Lenses

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WEEK 8:

TOPIC: APPLICATION OF LENSES (CONTD):

CONTENT:

• The Camera
• Comparing the human eye with the camera
• Simple and compound microscope
• Telescope
• Simple periscope (SEE APPLICATIONS MIRROR)
• film projector

THE CAMERA

The camera is a device for taking photographs of an object. It consists of

1. A light proof box with a converging lens in front of it and a light sensitive film at the back. The distance between the lens and the film can be varied so that objects in front of the lens can always be focused on the film by the converging lens.
2. A shutter of variable speed between the lens and the film to admit or shuts off light from the film.
3. An aperture that regulates the amount of light energy getting to the film
4. A diaphragm that regulates the size of the aperture

When taking a photograph of an object, the camera lens will be pointed at the object and the focusing ring is used to adjust the distance between the lens and the film until a sharp image of the object is obtained on the film. A button is then pressed so that the shutter quickly opens and closes, exposing the film, for a brief period to light from the object

Sub topic 2: Comparison of the human eye with camera

• Similarities between the human eye and camera

1. The human eye is impregnated with black pigment within while the camera consists of a light-tight box painted black inside
2. The human eye has the retina which is light sensitive. The camera has a film which is also light sensitive
3. Both have converging lens systems to focus light from an external object
4. The iris in human eye performs the same function as diaphragm in camera. i.e both regulates the amount of light entering the eye/camera respectively
5. The pupil in human eye performs the same function as the aperture in camera

Differences between the human eyes and the camera

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