iris - a band of muscle that controls the size of the pupil, which controls the amount of light entering the eye
pupil dilates to allow more light in (dim light)
constricts to let less light in (bright light)
aperture - whole where light comes into a camera
diaphragm - device that changes the size of the aperture
shutter - lies behind the aperture acts like a set of doors. The longer the shutter remains open, the more light enters the camera and strikes the film
diagram of camera
A) film
B) shutter
C) aperture
D) lens
retina - a layer that is filled with photoreceptors
photoreceptors - cells sensitive to light
rods - Highly sensitive to light, they can function in very low light
cones - less sensitive than rods but are responsible for colour vision
how images are formed
When light strikes the retina, the photoreceptors are stimulated
They send messages to the optic nerve (at the back of the eye)
The optic nerve then passes the message onto the brain
The brain then translates the message into an image
film - light sensitive material at the back of a camera, changes chemically
The images formed on both the retina and on the camera film are upside down (inverted)
focusing light
ciliary muscles attached to the lens contract and relax to change the shape of the lens
Changing the shape of the lens adjusts the focal length so that light forms a focused image on the retina
farsightedness - when people cannot see close objects clearly, images form to FAR behind the retina
nearsightedness - when people cannot see far things clearly
