Post on 06-Aug-2020
Refraction, Lenses, & Sight
• Copy all text underlined in red. Draw
sketches outlined in red.
Refraction • The change in direction of a wave as is crosses the
boundary between two media in which the wave
travels at different speeds.
Index of Refraction
materialinlightofspeed
vacuuminlightofspeedn
Snell’s Law 2211
sinsin nn
Index of Refraction Material Index of Refraction
Vacuum 1.0000
Air 1.0003
Ice 1.3100
Water 1.3330
Ethyl Alcohol 1.3600
Plexiglas 1.5100
Crown Glass 1.5200
Light Flint Glass 1.5800
Dense Flint Glass 1.6600
Zircon 1.9230
Diamond 2.4170
Rutile 2.9070
Gallium phosphide 3.5000
Dispersion
• The separation of light into colors arranged
according to their frequency, by interaction
with a prism or diffraction grating.
Rainbows • White light separates into different colors
(wavelengths) on entering the raindrop because red light is refracted by a lesser angle than blue light. On leaving the raindrop, the red rays have turned through a smaller angle than the blue rays, producing a rainbow.
STOP HERE
Lenses
Converging Lens
Rules For Converging Lenses
1) Any incident ray traveling parallel to the
principal axis of a converging lens will refract
through the lens and travel through the focal
point on the opposite side of the lens.
2) Any incident ray traveling through the focal
point on the way to the lens will refract through
the lens and travel parallel to the principal axis.
3) An incident ray which passes through the center
of the lens will in effect continue in the same
direction that it had when it entered the lens.
Image Formation by Converging Lens
Diverging Lens
Rules For Diverging Lenses
1) Any incident ray traveling parallel to the
principal axis of a diverging lens will refract
through the lens and travel in line with the focal
point (i.e., in a direction such that its extension
will pass through the focal point).
2) Any incident ray traveling towards the focal
point on the way to the lens will refract through
the lens and travel parallel to the principal axis.
3) An incident ray which passes through the center
of the lens will in effect continue in the same
direction that it had when it entered the lens.
Diverging Lens Image Formation
Always Virtual, Smaller, and Right-Side Up
The Human Eye
The Human Eye
Normal Eye Focus
Near-Sighted (Myopia)
Far-Sighted (Hypermetropia)
Astigmatism
• Cornea is oval shaped instead of spherical.
This causes light to focus on two or more
spots.
LASIK
Laser-assisted In Situ Keratomileusis