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The Eye and Cameras . How are our eyes and cameras similar to each other? . Starter: Look at the following optical illusions – what is going on!!! . Glossary . Pupil, iris, cornea, retina, optic nerve, cillary muscles, suspensory ligaments. The role of the eye.
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The Eye and Cameras How are our eyes and cameras similar to each other? Starter: Look at the following optical illusions – what is going on!!!
Glossary • Pupil, iris, cornea, retina, optic nerve, cillary muscles, suspensory ligaments
Light enters through the cornea • Light is focused on the retina where light sensitive cells are. • The Iris controls the size of the pupil – controls how much light enters. • The lens focuses light onto the retina.
Task • Label your eye diagram using page 220
The Eye and Lenses – a quick recap. How can we correct long and short sightedness? Starter: If I am short sighted I can see things that are …….
Focusing on objects • Close objects – you can only focus on things 25 or more cm away from your eyes. • This is the near point – if you are long sighted this gets further away. • Far objects – the limit is INIFINITY ….seriously. To focus, your ciliary muscles change the thickness of your lens. If you are close to an object you need a THICKlens and vise versa.
Lens power (what the opticians use) Power (dioptre) = 1/focal length in m +vee.g. 5.0 = you are long sighted and you have a Converging lens A negative value = -1.25 ( that’s what Miss Morris is ) you have a diverging lens. Miss Morris is Diverging!
Sight Defects Short Sighted Cant see far away. Image forms BEFORE the retina. Cause: Eye ball too long OR Lens too thick. Correction: use a diverging lens. Long sighted Cant see close up. Image forms after the retina. Cause: lens cannot be made thick enough. Correction: use a converting lens.
Similarities between cameras and eyes • BOTH • Use a converging lens • Form a real image • Invert the image • Amount of light can be controlled.