Uses of LensesUses of Lenses

November 7, 2012November 7, 2012

ObjectivesObjectives

1.1. Diagram the different types of Diagram the different types of lenseslenses

2.2. Describe the different uses of Describe the different uses of lenseslenses

3.3. Explain how lenses functionExplain how lenses function

Types of LensesTypes of Lenses concave lens – where light that concave lens – where light that

passes through diverges as if it came passes through diverges as if it came from a pointfrom a point

Convex lens – where light that Convex lens – where light that passes through converges to a single passes through converges to a single pointpoint

What are Lenses Used for?What are Lenses Used for?

1.1. Camera’sCamera’s

2.2. TelescopesTelescopes

3.3. Eyeglasses/ContactsEyeglasses/Contacts

Camera’sCamera’s Pinhole Camera:Pinhole Camera:

– Simplest of camera’sSimplest of camera’s– A box with a pinhole in the front and film A box with a pinhole in the front and film

paper attached to the backpaper attached to the back– Hole prevents overlapping rays and Hole prevents overlapping rays and

prints a very dim upside down imageprints a very dim upside down image

Improved lens CameraImproved lens Camera– Lens admits more light (takes less time)Lens admits more light (takes less time)– Allows more rays without overlapping Allows more rays without overlapping

(brighter more focused image) (brighter more focused image)

Explain in your own words Explain in your own words how this works.how this works.

The EyeThe Eye

How do the lenses in your eyes help How do the lenses in your eyes help you see?you see?

EyesightEyesight

Nearsighted – can’t see far awayNearsighted – can’t see far away Farsighted – can’t see close upFarsighted – can’t see close up

What is the importance of the rays What is the importance of the rays meeting at the retina?meeting at the retina?

Nearsighted VisionNearsighted Vision

The lens becomes shorter and fatterThe lens becomes shorter and fatter

Where do the rays come into focus?Where do the rays come into focus?

How can this be corrected?How can this be corrected?

Farsighted VisionFarsighted Vision

The lens becomes longer and The lens becomes longer and skinnierskinnier

Where do the rays come into focus?Where do the rays come into focus?

How can this be corrected?How can this be corrected?

How are camera’s and our How are camera’s and our eyes similareyes similar

TelescopesTelescopes

GalileoGalileo KeplerKepler

Galileo’s TelescopeGalileo’s Telescope

Kepler’s TelescopeKepler’s Telescope

Using a second concave lens Using a second concave lens magnified the image even moremagnified the image even more