The eye

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The Eye

Cornea --> Tough, transparent covering over the front part of the eye. Convex in shape. Refracts light as it enters the eye (by a fixed amount).

Iris --> Coloured part of the eye that contains muscles. These relax or contract to adjust the size of  the pupil. Controls how much light enters the eye.

Pupil --> Hole in the middle of the iris. Allows light to pass through as it enters the eye.

Lens --> Transparent, bi-convex, flexible disc behind the iris. It is attached to the ciliary muscles by the suspensory ligaments. Refracts light to focus it onto the retina. The amount of refraction can be adjusted by altering the thickness and curvature of the lens.

Ciliary Muscles --> Muscles connected to the lens by suspensory ligaments. Adjust the shape of the lens to make it more or less curved, so as to increase or decrease the refraction of light.

Retina --> The lining of the back of eye containing two types of light receptor cells. Rods are sensitive to dim light and black and white. Cones are sensitive to colour. Contains the light receptors, which trigger electrical impulses to be sent to the brain when light is detected.

Suspensory Ligaments -->Connect the ciliary muscles to the lens and hold the lens in place. Slacken or stretch as the ciliary muscles contract or relax, to adjust the thickness and curvature of the lens.

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Liquids are virtually incompressible --> you cant squash them, thier volume and density stay the same.

Pressure in a liquid is transmitted equally in all directions.

Pressure = Force / Cross sectional area

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Switch Mode

Type of transformer that operate at higher frequencies than traditional transformers.

Operate at between 50kHz and 200kHz.

Because they work at higher frequencies, they can be made much lighter and smaller than traditional transformers.

This makes them more useful in things like mobile phone chargers and power supplies.

More effiicent. They use very little power. When theyre switched on but no load is applied.

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