20,345
edits
Changes
→Finding the Focal Length
{| class="wikitable"
|-
|[[File:ConvexLens.png|center|200px100px]]|[[File:ConvexLensSymbol.png|center|200px100px]]
|-
| style="height:20px; width:200px; text-align:center;" |A picture of a '''convex lens'''.
| style="height:20px; width:200px; text-align:center;" |They The symbol used in [[diagram]]s to represent a '''convex lens'''
|}
===About Convex Lenses===
: A '''convex lens''' causes [[parallel]] [[Light Ray|rays]] of [[light]] to [[converge]], so it can also be called a [[Converging Lens|converging lens]].
: A '''convex''' [[lens]] is used to [[focus]] [[light]].
{| class="wikitable"
|-
|[[File:ConvexLensFocalPoint.png|center|500px]]
|-
| style="height:20px; width:200px; text-align:center;" |A '''convex lens''' [[focus|focuses]] [[parallel]] [[Light Ray|rays]] to a [[Focal Point|focal point]].
|}
==Key Stage 4 Higher==
===Meaning===
A '''convex''' [[lens]] is a shaped piece of [[glass]] that is thickest at the centre and thinnest at the edges.
{| class="wikitable"
|-
|[[File:ConvexLens.png|center|100px]]
|[[File:ConvexLensSymbol.png|center|100px]]
|-
| style="height:20px; width:200px; text-align:center;" |A picture of a '''convex lens'''.
| style="height:20px; width:200px; text-align:center;" |The symbol used in [[diagram]]s to represent a '''convex lens'''
|}
===About Convex Lenses===
: A '''convex lens''' causes [[parallel]] [[Light Ray|rays]] of [[light]] to [[converge]], so it can also be called a [[Converging Lens|converging lens]].
: A '''convex''' [[lens]] is used to [[focus]] [[light]].
: Projecting an [[image]] onto a [[screen]] using a '''convex [[lens]]''' creates a [[Real Image|real image]]. Looking through a '''convex [[lens]]''' the [[image]] seen is a [[Virtual Image|virtual image]].
: When the [[Object Distance|object distance]] is greater than the [[Focal Length|focal length]] of a '''convex [[lens]]''' the [[image]] produced is [[diminished]] and [[inverted]] (upside down and back to front).
: When the [[Object Distance|object distance]] is less than the [[Focal Length|focal length]] of a '''convex [[lens]]''' the [[image]] produced is [[magnified]] and the right way up.
===Finding the Focal Length===
{| class="wikitable"
|-
|[[File:ConvexLensFocalPoint.png|center|500px]]
|-
| style="height:20px; width:200px; text-align:center;" |A '''convex lens''' [[focus|focuses]] [[parallel]] [[Light Ray|rays]] to a [[Focal Point|focal point]].
|}
: The [[Focal Length|focal length]] of a '''convex lens''' is the distance between the [[Focal Point|focal point]] and the centre of the [[lens]].
{| class="wikitable"
|-
|[[File:FocalLength.png|center|500px]]
|-
| style="height:20px; width:200px; text-align:center;" |A [[diagram]] showing how to find the [[Focal Length|focal length]] of a '''convex [[lens]]'''.
|}
To find the [[Focal Length]] of a '''convex [[lens]]''':
*[[Focus]] the [[image]] of a "distant object" onto a [[screen]].
*[[Measure]] the [[distance]] between the [[lens]] and the [[screen]].
The [[Image Distance|image distance]] (the distance between the [[focus]]sed [[image]] and the [[lens]]) is the same as the [[Focal Length|focal length]] for a "distant object".
If the [[Object Distance|object distance]] (the distance between an [[object]] and a [[lens]]) is too small, then the [[Image Distance|image distance]] is not the same as the [[Focal Length|focal length]].
===Ray Diagrams===
{| class="wikitable"
|-
|[[File:ConvexRayDiagram1.png|center|600px]]
|-
| style="height:20px; width:200px; text-align:left;" |A [[Ray Diagram|ray diagram]] for a '''convex [[lens]]'''.
In this [[diagram]]:
"Ray 1" is shown crossing the [[Focal Point|focal point]] of the [[lens]] after being [[refract]]ed.
"Ray 2" is shown passing through the centre of the [[lens]].
"Ray 3" is shown crossing the [[Focal Point|focal point]] before the [[lens]].
The [[diagram]] shows that a [[diminish]]ed [[Real Image|real image]] is produced when the [[Object Distance|object distance]] is greater than the [[Focal Length|focal length]] of the '''convex [[lens]]'''.
|}
{| class="wikitable"
|-
|[[File:ConvexRayDiagram1.png|center|300px]]
|[[File:ConvexRayDiagram2.png|center|300px]]
|-
| style="height:20px; width:200px; text-align:center;" colspan = "2" |Comparing these two [[diagram]]s shows that the [[image]] size increases as the [[Object Distance|object distance]] approaches the [[Focal Length|focal length]] of the [[lens]].
|}
===Magnification===
For further details, see [[magnification]].
The equation for the [[magnification]] of a '''convex [[lens]]''' is:
Magnification = (Image Length)/(Object Length)
<math>Magnification = \frac{L_i}{L_o}</math>
Where
<math>{L_i}</math> = Length of the [[image]].
<math>{L_o}</math> = Length of the [[object]].
===References===
====AQA====
:[https://www.amazon.co.uk/gp/product/019835939X/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=019835939X&linkCode=as2&tag=nrjc-21&linkId=57e96876985fc39b1a3d8a3e3dc238b6 ''Convex lenses, page 208, 211, GCSE Physics; Third Edition, Oxford University Press, AQA '']
:[https://www.amazon.co.uk/gp/product/1471851370/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1471851370&linkCode=as2&tag=nrjc-21&linkId=01c69b0ae058f809cf636033e6ba793e ''Convex lenses, pages 203-4, GCSE Physics, Hodder, AQA '']
:[https://www.amazon.co.uk/gp/product/1782945970/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945970&linkCode=as2&tag=nrjc-21&linkId=a120d24dcc7cc7a58192069a3aafc1d2 ''Convex lenses, pages 266, 267, 270-272, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA '']
:[https://www.amazon.co.uk/gp/product/178294558X/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=178294558X&linkCode=as2&tag=nrjc-21&linkId=f0dfb66dafcb0c6e9449e7b1a4ae1ac71 ''Convex lenses, pages 82-84, GCSE Physics; The Revision Guide, CGP, AQA '']
:[https://www.amazon.co.uk/gp/product/1471851370/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1471851370&linkCode=as2&tag=nrjc-21&linkId=01c69b0ae058f809cf636033e6ba793e ''Convex lenses; magnifying glasses, pages 205-6, GCSE Physics, Hodder, AQA '']
:[https://www.amazon.co.uk/gp/product/1471851370/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1471851370&linkCode=as2&tag=nrjc-21&linkId=01c69b0ae058f809cf636033e6ba793e ''Convex lenses; ray diagrams, pages 204-5, GCSE Physics, Hodder, AQA '']
:[https://www.amazon.co.uk/gp/product/1471851370/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1471851370&linkCode=as2&tag=nrjc-21&linkId=01c69b0ae058f809cf636033e6ba793e ''Convex lenses; refraction of light, page 203, GCSE Physics, Hodder, AQA '']
====Edexcel====
:[https://www.amazon.co.uk/gp/product/1782948163/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782948163&linkCode=as2&tag=nrjc-21&linkId=0fdbfd5dd397d6e24a9dfb250f08587f ''Converging lenses, page 118, GCSE Physics, CGP, Edexcel '']
:[https://www.amazon.co.uk/gp/product/1782945733/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945733&linkCode=as2&tag=nrjc-21&linkId=2a2dbec9db6bf5766c0458d908fa0a52 ''Converging lenses, pages 41, 42, GCSE Physics; The Revision Guide, CGP, Edexcel '']
:[https://www.amazon.co.uk/gp/product/1292120223/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1292120223&linkCode=as2&tag=nrjc-21&linkId=068ecf40278c32406a7f1c6e66751417 ''Converging lenses, pages 70, 71, GCSE Physics, Pearson Edexcel '']
:[https://www.amazon.co.uk/gp/product/1782948163/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782948163&linkCode=as2&tag=nrjc-21&linkId=0fdbfd5dd397d6e24a9dfb250f08587f ''Converging lenses; images, page 124, GCSE Physics, CGP, Edexcel '']
:[https://www.amazon.co.uk/gp/product/1782948163/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782948163&linkCode=as2&tag=nrjc-21&linkId=0fdbfd5dd397d6e24a9dfb250f08587f ''Converging lenses; ray diagrams, pages 122, 123, GCSE Physics, CGP, Edexcel '']