10.7 lenses

10.7 THIN CONVEX lensesAlso called, why the human eye is spherical instead of flat.

Ever wondered?

ObjectivesWWBATDescribe how an image is formed by a thin convex lensDetermine the location of image formation for a thin convex lensDetermine the magnification of an image for a thin convex lensDetermine whether or not an image is upright or inverted for a thin convex lensDetermine whether an image is real or virtual for a thin convex lens

Image formation by refractionin thin convex lensesConvex: bending outwardThin convex lenses are also called biconvex or convergingLight rays from an object are refracted and converge to form a real image beyond the lens

Focal lengthThe focal length of a thin convex lens is the point beyond the lens where all head-on light rays converge when refractedThis is not where the image forms, however!

How to predict image formation for thin convex lensesQuestions to askWhere does the image form?Is the image upright or inverted (upside down)?Is the image larger or smaller than the original image?

Ray Diagramsfor thin convex lenses

Ray Diagramsfor thin convex lenses

Ray Diagramsfor thin convex lenses

Ray Diagramsfor thin convex lenses

Ray Diagramsfor thin convex lensesCheck out the PhET Virtual Lab on the course website!

A tricky example

A tricky example

A tricky example

An even trickier example

The Five CasesImage beyond 2FImage at 2FImage between F and 2FImage at FImage closer to lens than FReal image

Inverted

SmallerReal image

Inverted

Same sizeReal image

Inverted

LargerNo image formsVirtual image

Upright

Larger

Check yourself #1

Check yourself #1

Math of image formation

Math of image formation

Possible OutcomeWhat it meansdi is negativeVirtual image; image forms on same side of lenshi or M is negativeReal image (inverted)

A 4.00-cm tall light bulb is placed a distance of 45.7 cm from a double convex lens having a focal length of 15.2 cm. Determine the image distance and the image size.

A 4.00-cm tall light bulb is placed a distance of 45.7 cm from a double convex lens having a focal length of 15.2 cm. Determine the image distance and the image size.

A 4.00-cm tall light bulb is placed a distance of 45.7 cm from a double convex lens having a focal length of 15.2 cm. Determine the image distance and the image size.

A 4.00-cm tall light bulb is placed a distance of 45.7 cm from a double convex lens having a focal length of 15.2 cm. Determine the image distance and the image size.

You Try4.00-cm tall light bulb is placed a distance of 8.30 cm from a double convex lens having a focal length of 15.2 cm. (NOTE: this is the same object and the same lens, only this time the object is placed closer to the lens.) Determine the image distance and the image size.

You Try4.00-cm tall light bulb is placed a distance of 8.30 cm from a double convex lens having a focal length of 15.2 cm. (NOTE: this is the same object and the same lens, only this time the object is placed closer to the lens.) Determine the image distance and the image size.

ObjectivesWWBATDescribe how an image is formed by a thin convex lensDetermine the location of image formation for a thin convex lensDetermine the magnification of an image for a thin convex lensDetermine whether or not an image is upright or inverted for a thin convex lensDetermine whether an image is real or virtual for a thin convex lens

Still want more?Extra resources on the website about how the eye works!