C: Light and Optical Systems, section 4: eyes and cameras Flashcards
What is the function of the cornea?
Protect all the sensitive parts of the eye
What is the function of the iris?
To control the size of the pupil
What is the function of the pupil?
To let in more or less light
What is the function of the ciliary muscle?
To make the lens thicker or thinner
What is the function of the lens?
To focus the light onto the retina
What is the purpose of the retina?
To send the image to the optic nerve
What is the function of the optic nerve?
To send the image to the brain
What does it mean when the pupil dilates?
Becomes bigger
Which part of the camera is like the retina?
The film
What part of the camera is like the iris?
The diaphragm
What part of the camera is like the eyelid?
The shutter
What part of the camera is like the lens?
The lens!
What part of the camera is like the pupil?
The aperture
What is the retina?
It is the sensitive layer that light strikes. It is filled with photo receptors
What are rods sensitive to?
Light
What are cones sensitive to?
colour
Why can’t you see colours in darker environments but still see?
Because cones don’t work very well in low light
What happens when light strikes the retina?
The photoreceptors send light to the optic nerve
What is farsightedness?
When the light doesn’t focus early enough
What is nearsightedness?
When the light focuses to early
How is farsightedness corrected?
It is fixed with convex lenses
How is nearsightedness corrected?
It is fixed with concave lenses
How does laser eye surgery work?
The surgeon uses a laser to reshape the cornea
How do night vision goggles work?
Light goes through light intensifiers and then through a phosphor screen which causes them to glow green
What is the difference between phosphorus and phosphor?
A phosphor is a chemical compound that emits light when it is exposed to light of a different wavelength (i.e. colour). Phosphors do not contain the chemical element Phosphorus, which can be made to glow a different way. This sometimes causes confusion.
Phosphors are usually made from a suitable host material with an added activator. The best known type is a copper-activated zinc sulfide (ZnS) and the silver-activated zinc sulfide (zinc sulfide silver).
