8381958
Description
Flashcards by david doran, updated more than 1 year ago
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Created by david doran
over 7 years ago
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| Question | Answer |
| State the function of the retina | the light sensitive cells around the inside of the eye |
| State the function of the lens | focuses light onto the retina |
| State the function of the cornea | transparent layer that protects the eye and helps to focus light onto the retina |
| State the function of the pupil/iris | pupil: the central hole formed by the iris. Light enters the eye through the pupil iris: coloured ring of muscle that controls the amount of light entering the eye |
| State the function of the ciliary muscle | attached to the lens by suspensory ligaments. the muscles change the thickness of the eye lens |
| How is the shape of the lens changed | |
| what causes long sightedness and how is it corrected | long sight, caused by the eyeball being too short, so rays of light are focussed behind the retina. We use a converging lens to correct it |
| what causes short sightedness and how is it corrected | short sight, caused by the eyeball being too long, so rays of light are focussed in front of the retina .we use a diverging lens to correct it |
| What is the range of vision | from 25cm to infinity |
| how does refractive index of the glass effect the shape of a correcting lens | the higher the refractive index of the glass used to make a corrective lens the flatter and thinner the lens can be |
| state 2 factors the effect the focal length of a lens | The focal length of a lens is determined by: ■ the refractive index of the material from which the lens is made, and ■ the curvature of the two surfaces of the lens. |
| compare the structure of the eye and a camera | Like the eye, the image produced by a camera is diminished, inverted and real.One key difference between a camera and the eye is that a camera does not focus light onto the photosensitive surface by adjusting the shape of the lens. Instead, the focusing screws move the lens forwards or backwards in order to focus the image onto the photosensitive surface. |
| How do you calculate the power of a lens and state the difference between the power of a converging lens and diverging lens | P is power in dioptres, D f is focal length in metres, m the power of a converging lens is positive and the power of a diverging lens is negative |
| what in a camera is the equivalent of the retina in the eye | the film in a camera or the CCDs in a digital camera is the equivalent of the retina in the eye |
| how does the eye adapt in bright light | the circular muscles of the iris contract making the pupil smaller |
| how does the eye adapt in darkness | the circular muscles of the iris relax making the pupil larger |
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