lenses. applications of light refraction what are some common applications of the refraction of...
TRANSCRIPT
Lenses
Applications of Light Refraction• What are some common
applications of the refraction of light?
• Cameras• Microscopes• Lenses• Eyeglasses• Human eye• Telescopes• Binoculars
Lenses
• Definition: curved piece of glass• When light passes through as lens,
direction of light changes• Each light ray strikes surface of lens at
slightly different angle• Two types: 1) Converging lens:
– Bends light inward– Ex: magnifying glass
2) Diverging lens:– Bends light outward
Lenses
• Compound microscope uses multiple lenses to magnify an object
• Magnification: any change in the size of an image compared with the size of the object
The Human Eye
• Without refraction, we couldn’t see at all!• Human eye works similar to a camera
Camera vs. Human Eye
• Light enters through large lens
• Lens focuses light• Light creates image
on film at back of camera
• Light enters eye through cornea (transparent tissue)
• Light passes through pupil (hole in iris)
• Light travels though lens which focuses image on retina (back layer of eye)
The Anatomy of the Human Eye
• Cornea:– Where light first enters
eye– Responsible for 70% of
refraction of light in eye
• Lens:– Curvature determines
refraction of light– Muscles adjust curvature
of lens
The Anatomy of the
Human Eye
• Retina:– Made up of light sensitive cells, rods and cones
• When light strikes rods and cones, signals sent to brain where they are interpreted as images
– Cones: responsible for color vision• Only respond to bright light• Why we can’t see color in very dim light
– Rods: sensitive to dim light• Can’t resolve details well
Eye Defects
• Near-sightedness (also called myopia)
• Common cause of blurred vision
• Objects in the distance appear blurry and out of focus
• Caused by change in the shape of the eyeball that makes the eyeball oval (egg-shaped) rather than round
Near-Sightedness• Causes light rays entering the eye to focus in
front of retina
Far-Sightedness
• Also called hyperopia
• Can clearly see objects that are far away, but they have trouble seeing objects up close
• Occurs when eye is too short lengthwise
• This causes an image to focus behind the retina
Far-Sightedness
Concave Lens vs. Convex Lens
• Convex: bends light inward
• Concave: bends light outward
Lenses can be used to correct vision defects
• Near-sightedness (right) Concave lens• Far-sightedness (left) Convex lens