Physics Chapter 30: Lenses

what condition must exist for a diverging lens to produce a real image

A DIVERGING LENS CAN NEVER PRODUCE A REAL IMAGE. image is always right side up, virtual and smaller. the distance doesn't matter.

the real image produced by a converging lens is inverted. our eyes have converging lenses. does this mean the images you see are upside down on your retinas? Explain.

Image on the back of our eye must be upside down because converging lens is letting light through the light through from far away

astigmatism

a defect in the eye caused when the cornea is curved more in one direction than the other

convex lens

a lens that is thickest in the middle causing parallel rays of light to converge to a focus. Also known as a converging lens.

converging lens

a lens that is thickest in the middle causing parallel rays of light to converge to a focus. Also known as a convex lens.

diverging lens

a lens that is thinnest in the middle and causes parallel rays of light to diverge. Also known as a concave lens.

concave lens

a lens that is thinnest in the middle and causes parallel rays of light to diverge. Also known as a diverging lens.

lens

a piece of glass that can bend parallel rays of light so that they cross or appear to cross at a single point

what kind of image forms on the back of your eye (and on the film of a camera)

a real image

a. in which case does light under go the greatest change in speed? b. in which case is refraction greater?

a. travelling in air and entering glass b.air to glass

blind spot

area where a person's view is obstructed

accomodation

automatic adjustment of focus of the eye by flattening or thickening of the lens

describe the difference in focusing with a camera and how the eye focuses.

camera focuses by moving lens back and forth and uses a shutter. the eye focuses when shape and thickness of lens change by ciliary muscles.

compare the parts of the eye and the parts of an image

camera________eye shutter_________eyelid diaphragm_____iris aperture_______pupil convex lens____convex lens film____________retina

explain the cause and correction for nearsightedness

cause- the eyeball is too long, image forms in front of retina correction- diverging lenses

explain the cause and correction for astigmatism

cause-abnormally shaped cornea correction- cyllinder shaped lens

explain the cause and correction for farsightedness

cause-eyeball is too short, causing image to form behind the retina correction-converging lenses

iris

colored part of eye that surrounds black opening through which light passes. regulates amount of light entering the eye

ray diagram

diagram showing that can be drawn to determine size and location of an image formed by mirror of lens

focal length

distance between center of lens and either focal point

aberration

distortion in an image that is produced by a lens

focal point

for a converging lens, the point where a beam of light parallel to the principal axis converges. for a diverging lens, the point from which such a beam appears to come.

real image

image formed by converging light rays and can be displayed on a screen

virtual image

image formed through reflection or refraction that can be seen by an observer but not projected on a screen because the light from an object doesn't actually come to focus

Where does no ending of light occur when it passes through the lens?

in the middle

retina

layer of light sensitive tissue at back of eye

eyepiece

lens of telescope closest to eye; enlarged real image formed by first lens

name four common optical instruments other than eyeglasses

magnifying glass, camera, telescope, microscope

pupil

opening in eyeball through which light passes

objective lens

optional device using compound lenses, the lens closest to object observed

focal plane

plane passing through either focal point of a lens that is perpendicular to principal axis. for a converging lens, incident parallel beam of light converges to point on focal plane. for a diverging lens, beam of light appears to come from a point on the focal plane.

What type of image can be projected onto a screen?

real image

Describe the orientation of a real image and a virtual image compared to the original object viewed.

real image- upside down virtual image- right side up

fovea

small depression in retina where visual acuity is high

nearsighted

term applied to a person who can clearly see nearby objects but not clearly see distant objects. the eyeball is too long so images focus in front of rather than on the retina.

farsighted

term applied to a person who has trouble focusing on nearby objects because the eyeball is so short that images form behind the retina

principal axis

the line joining the curvature of the surface of a lens

what condition is necessary for a converging lens to form a real image?

the object must be beyond the focal point

cornea

transparent covering over the eye

how many rays are needed to locate an image

two, doesn't matter which lens

a.when does a converging lens act as a magnifying glass b. what kind of image does the converging lens form in this situation

when the object is between the focal point and the lens b. virtual and enlarged