# Understanding Lenses in Optics

This Grade Science Unit on Optics focuses on the chapter of Lenses, which explains how lenses refract light to form images. Lenses are curved pieces of transparent material, usually made from glass

## About Understanding Lenses in Optics

PowerPoint presentation about 'Understanding Lenses in Optics'. This presentation describes the topic on This Grade Science Unit on Optics focuses on the chapter of Lenses, which explains how lenses refract light to form images. Lenses are curved pieces of transparent material, usually made from glass. The key topics included in this slideshow are . Download this presentation absolutely free.

## Presentation Transcript

Slide1Grade 8  Science Unit  2:  Optics Grade  8  Science Unit  2:  Optics Chapter 6 : Lenses refract light to form images.

Slide2LensesLenses  A curved piece of transparent material that refracts light in a predictable way.  Usually made from glass or plastic.

Slide3Lenses

Slide4There are two types oflenses: 1. Convex  Centre of the lens bulges out  Causes light rays to bend toward each other ( converge )

Slide52. Concave Centre of the lens is curved in  Causes light rays to bend away from each other ( diverge )

Slide7Convex Lenses Convex  Lenses  Can act as a magnifying glass  Each lens has its own focal length ( the distance from the centre of the lens to the focal point )

Slide8The greater the curvature of the lens, the shorter the focal length. ( pg. 217 )

Slide9Lenses have focal points on either side because light shines through either side.  The line through the centre of the lens is called the principle axis .  Optical centre  is where the principle axis meets the lens centre.

Slide10PrincipleAxis Optical Centre

Slide11Concave Lenses Concave  Lenses  To find the focal point, you must extend the refracted rays back.

Slide12Lenses with the greater curvature have the shortest focal length. ( pg. 221 )

Slide13Corrective Lenses Corrective  Lenses The Eye (pg. 229)

Slide14Vision

Slide15Near-sighted Vision Near-sighted  Vision  See objects up close but not at a distance.  Concave lenses are used to correct this vision.

Slide16Near- sighted Vision

Slide17Far-sighted Vision Far-sighted  Vision  See objects at a distance but not up close.  Convex lenses are used to correct this vision.

Slide18Far-sighted Vision

Slide19Determining Focal Length...You must include the following incident rays: 1. Travelling parallel to the p.a. 2. Travelling through the o.c. 3. Travelling through the F.

Slide20Ray Diagrams:  Convex  Lenses Ray  Diagrams:  Convex  Lenses Object between the lens and focal point.

Slide21Object is between the focalpoint and 2X the focal length.

Slide22Object is more than 2X thefocal length.

Slide23Ray Diagrams:  Concave  Lenses Ray  Diagrams:  Concave  Lenses The above is true for an object in all positions.

Slide24CORESTSE: “Fibre Optics” Fibre Cable

Slide25Optical Technologies... Optical  Technologies... 1. Microscopes  Uses  two  convex lenses with relatively short focal points to magnify  Magnified twice to increase enlargement

Slide26The Microscope

Slide272. Telescopes The objective lens has a longer focal length than the microscope.  Can have either a refracting or reflecting telescope

Slide28Refracting Telescope  (pg.  245) Refracting  Telescope  (pg.  245)  The lenses bend light to focus it.  The objective lens must be as large as possible to view distant galaxies (makes it heavy)

Slide29Reflecting Telescope  (pg.  246) Reflecting  Telescope  (pg.  246)  Uses a concave mirror, plane mirror and a convex lens to collect and focus light from objects at a great distance.  Most large telescopes are this type.

Slide30The Hubble Space TelescopeLaunched in 1990

Slide31The ReflectingTelescope

Slide323. Cameras (pg. 248)4. Binoculars (pg. 247) 5. Face shields 6. Magnifying glasses 7. Contact lenses 8. Flashlights 9. Eye glasses

Slide33The Nature  of  Science The  Nature  of  Science  The development of new technologies involve many individuals and groups of people.  These technologies can alter what we know about the nature of science.

Slide3416021672 Individuals... Galileo Newton

Slide35Groups...