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HOW WE USE LIGHT 



the rear. The retina is connected to the brain by the 

 optic nerve. The lens is capable of changing its shape, 



-lens 



film... 



What parts of the camera correspond to the parts of the eye ? 



thus making it possible to focus the light and so make a 

 real image of near or distant objects on the retina. This 

 change of focus is called accommodation. A colorless fluid 

 fills the space between the lens and the retina. The 

 retina is the most wonderful part of the eye because it 

 transfers the sensations produced by light in the eye to 

 the brain by way of the optic nerve. 



How the Eye Adapts Itself to Different Intensities of 

 Light. The diaphragm in the camera changes the size 

 of opening through which light may enter. The eye has 

 a similar device, but it is called the iris. The black spot 

 you see as the pupil of the eye is the opening through 

 which light passes to the lens. If you go to the window 



when there is bright 

 sunlight and look 

 steadily at the sky 

 for a moment, and 

 then bring a mirror 

 before your eye you 

 will see that the size 

 of the pupil or black 

 hole in the colored 

 iris is extremely small. If you turn quickly to a dark 

 part of the room and look in the mirror, you will see 

 the pupil grow larger as the iris adjusts itself to the 



How does the eye adjust itself to different 

 intensities of light? Which of the two eyes is 

 looking into a bright light ? How do you know ? 



