How are our eyes and cameras similar to each other? 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

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 THICK lens and vise versa.

Lens power (what the opticians use) Power (dioptre) = 1/focal length in m +ve e.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 Long sighted 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.

Correcting short and long sight

Similarities between cameras and eyes BOTH Use a converging lens Form a real image Invert the image Amount of light can be controlled.

Past paper Questions