Physics Lenses
What happens w/ near-sightedness?
Light rays focus on front of retina Can see things near but not far away Correct w/ Concave lens
What happens when light rays travel from air into glass in terms of direction and speed?
Light rays travel towards normal, and the light rays travel slower.
What happens when a light ray is traveling from air to plastic?
Angle of refraction is 2/3 the angle of incidence
What happens when a light ray is traveling from plastic to air?
Angle of refraction is 3/2 of angle of incidence
What is image of convex lens when object beyond 2F?
B/w F + 2F Real Inverted Smaller
What is Refraction?
Bending of light as it passes through a transparent material.
What is image of convex lens b/w 2F + F?
Beyond 2F Real Inverted Larger
What happens w/ Far-sightedness?
Light rays focus behind retina Far sighted person can see things far away but not things that are near Correct w/ convex lens
What happens when light enters a less dense material?
Speed is faster and it bends away from normal
What happens when light enters a more dense material?
Speed is slower and it bends towards the normal line
What must f be measured in when finding power of lens?
f must b measured in meters
What is image of convex lens at 2F?
@ 2F Real Inverted Same Size
If you are near-sighted what lens is in your glasses?
Concave lens
What type of lens is most similar to the lens in the human eye?
Convex lens w/ flexible focal length to see objects both near and far.
If you are far-sighted what lens is in your glasses?
Convex lenses
What are bifocals?
Correct both near + far sightedness. Top lens for far vision (near sightedness) and bottom lens for near vision (far sightedness).
What is unit of power?
Diopters (D)
What is caused by refraction?
Distorts underwater views, making straight objects appear bend, and making submerged objects appear shallower than the are
What are applications of total internal reflection?
Fiber optic cables (thin glass + plastic fibers) transmit light w/out much loss because of total internal reflection Used in telecommunication + medicine
How does the human eye allow for us to see?
Image formed on retina is upside down Your brain is able to correctly interpret image
What happens to size of image when you increase diameter of convex lens?
Image height remains unchanged, but image gets brighter.
What happens to an image when part of convex lens is covered?
Image is still there but not as bright
What is a real image in terms of lens?
Located on opposite side of lens w/ respect to object Can b projected on screen
What is a virtual image in terms of lens?
Located on same side of lens as object Can not b projected on screen
What is image of convex lens @ F?
No image
What is equation for power of lens?
P=1/focal length
What is meant by the critical angle?
Point in which light can not bend anymore therefore it skims the surface/boundary of two materials
What are characteristics of lens diagram?
Principal Optical Axis=P Optical Center: O 2 Radii of Curvature:R 2 Focal Points: F Sometimes Use 2F instead of C
What is index of refraction?
Ratio of speed of electromagnetic waves in vaccum (c) and speed of electromagnetic waves in given material n=c/v
What happens w/ Rays in convex lens?
Rays converge
What happens w/ Rays in concave lens?
Rays diverge
What type of image does convex lens produce?
Real or Virtual
What does the observation of a pencil demonstrate?
Refraction
What are convex lenses?
Thicker at center than edges
What are concave lenses?
Thinner @ center than edges
What type of image does concave lens produce?
Virtual
What is image of convex lens b/w F + O?
Virtual Upright Magnified
What is image of concave lens in front of O?
Virtual, Upright, and Smaller
What can b learned from Plexiglas block?
We can use pins to determine path of light through the block. Angle of incidence is larger than the angle of refraction, proving that light bends
When does light no bend?
When light enters along normal
What is total internal reflection?
When light travels from more dense to less dense material, it bends away from normal line. Eventually it can't bend away any more + it skims surface/boundary of two materials @ critical angle For angles greater than critical angle, internal reflection occurs, in other word light reflects back into material