Thin Lenses (Physics 2)

lenses / lens

a transparent object that refracts light rays such that the light rays converge or diverge to create an image

with curved surfaces, the direction of the normal line

differs for each spot on the medium

when light passes through a medium that has one or more curved surfaces,

the change in the direction of the light rays varies from point to point

real images form when

rays of light actually intersect to form the image

virtual images form when

a point from which light rays appear to come but do not actually come

real images __ be projected

can

virtual images ____ be projected

can not

a typical lens consists of a piece of glass or plastic ground so that each of its surfaces is a

segment of either a sphere or plane

converging lens

the lens that is thicker in the middle than it is at the rim

diverging lens

the lens that is thinner at the middle than it is at the rim

focal length (f)

the distance from the focal point to the center of the lens

the focal length is the image distance

that corresponds to an infinite object distance

lenses have two focal points, one on each side of the lens because

light can pass through the lens from either side

rays parallel to the principal axis diverge after

passing through a diverging lens

the focal point is defines as

the point from which the diverging rays appear to originate

refraction occurs at

a boundary between two materials with different indexes of refraction

thin lenses can have their front and back boundaries represented as

a line segment passing through the center of the lens

from the definition of a focal point,

we know that light traveling parallel to the principal axis will be focused at the focal point

for converging lens, the light will come together at

the focal point in the back of the lens

the front of the lens is defined as the

side of the lens that light rays first encounter

the back of the lens refers to the

side of the lens opposite where the light rays first encounter the lens

a ray passing through the center of the lens will continue in

a straight line with no net refraction

an object infinitely far away from a converging lens will create

a point image at the focal point distance and the image will be real

as a distant object approaches the focal point distance,

the image becomes larger and farther away

when an object is at the focal point,

the light rays from the object are refracted so they exit the lens parallel to each other

when an object is between a converging lens and its focal point,

the light rays from the object diverge when they pass through the lens

a diverging lens creates a

virtual image of a real object places anywhere with respect to the lens

thin-lens equation

the equation that relates object and image distances for a lens (when the lens thickness is much smaller than its focal point)

thin-lens equation

1/p + 1/q = 1/f

the thin-lens equation can be applied to both

converging and diverging lenses if we adhere to a set of sign conventions

an object in front of the lens, or an image in the back of the lens that is a real image, has a

positive object distance

an object in the back of the lens, or a virtual object,

has a negative object distance

a converging lens has a

positive focal length

a diverging lens has a

negative focal length

positive lenses

converging lenses

negative lenses

diverging lenses

magnification of a lens

M = -q/p

magnification will describe the

image’s size and orientation

when the magnitude of the magnification of an object is less than one,

the image is smaller than the object

when the magnitude of the magnification is greater than one,

the image is larger than the object

a negative sign for the magnification indicates that

the image is real and inverted

a positive magnification signifies that

the image is upright and virtual