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Curved MirrorsCurved Mirrors
Types of curved mirrors:Types of curved mirrors:
Concave mirrorConcave mirror– A mirror whose reflecting A mirror whose reflecting
surface curves inward – surface curves inward – Converging mirrorConverging mirror
Convex mirrorConvex mirror– A mirror whose reflecting A mirror whose reflecting
surface curves outward – surface curves outward – Diverging mirrorDiverging mirror
DefinitionsDefinitions
Center of Curvature (C)Center of Curvature (C)– Center of a sphere whose surface has been Center of a sphere whose surface has been
used as a mirrorused as a mirror
C = 2fC = 2f
Principal axis (P.A.)Principal axis (P.A.)– The line through C that passes through the midpoint of the The line through C that passes through the midpoint of the
mirror (normal to the centre of the mirror)mirror (normal to the centre of the mirror)
Vertex (V)Vertex (V)– The point where the P.A. meets the mirrorThe point where the P.A. meets the mirror
Focal Point (F)Focal Point (F)– Is halfway between the vertex and the center of curvature. Is halfway between the vertex and the center of curvature.
When parallel light rays are shone along the P.A., the When parallel light rays are shone along the P.A., the reflected rays converge and cross at the focal point.reflected rays converge and cross at the focal point.
Focal length (f)Focal length (f)– The distance from the focal point to the vertexThe distance from the focal point to the vertex
ConvergeConverge– To meet at a common pointTo meet at a common point
Rules for the construction of ray Rules for the construction of ray diagrams:diagrams:
1.1. Parallel rays are reflected through FParallel rays are reflected through F
2.2. Rays passing through F are reflected Rays passing through F are reflected parallel to the P.A.parallel to the P.A.
3.3. Rays passing through C are reflected Rays passing through C are reflected back along the same pathback along the same path
4.4. Rays striking V follow the laws of Rays striking V follow the laws of reflection (angle of incidence = angle of reflection (angle of incidence = angle of reflection)reflection)
Ray Diagrams are used to find the Ray Diagrams are used to find the Image of an ObjectImage of an Object
How to draw a Ray Diagram for a How to draw a Ray Diagram for a concave mirrorconcave mirror
1. Draw a horizontal line (P.A). Mark a Center of curvature, C, and draw a curve using a compass. Mark focal point, F, half way between C and V.
How to draw a Ray Diagram for a How to draw a Ray Diagram for a concave mirrorconcave mirror
2. Draw the object with its base on the P.A.
1. Draw a horizontal line (P.A). Mark a Center of curvature, C, and draw a curve using a compass. Mark focal point, F, half way between C and V.
How to draw a Ray Diagram for a How to draw a Ray Diagram for a concave mirrorconcave mirror
3. Draw the first Ray from the top of the object parallel to the P.A. Its reflecting ray will pass through F.
How to draw a Ray Diagram for a How to draw a Ray Diagram for a concave mirrorconcave mirror
4. Draw the second ray from the top of the object through F, its reflecting ray will travel parallel to the P.A.
3. Draw the first Ray from the top of the object parallel to the P.A. Its reflecting ray will pass through F.
How to draw a Ray Diagram for a How to draw a Ray Diagram for a concave mirrorconcave mirror
4. Draw the second ray from the top of the object through F, its reflecting ray will travel parallel to the P.A.
5. Draw a third ray through C, it will reflect back upon itself (because it is a normal)
3. Draw the first Ray from the top of the object parallel to the P.A. Its reflecting ray will pass through F.
How to draw a Ray Diagram for a How to draw a Ray Diagram for a concave mirrorconcave mirror
6. Draw the top of the image where the reflective rays intersect. The bottom of the image will be at the P.A.
How to draw a Ray Diagram for a How to draw a Ray Diagram for a concave mirrorconcave mirror
**Note: you only need 2 intersecting Rays in order to find the image**
6. Draw the top of the image where the reflective rays intersect. The bottom of the image will be at the P.A.
How to draw a Ray Diagram for a How to draw a Ray Diagram for a concave mirrorconcave mirror
What is the LOST for this image?
How to draw a Ray Diagram for a How to draw a Ray Diagram for a concave mirrorconcave mirror
What is the LOST for this image?L – in front of the mirror (b/w C and F)O – invertedS – smallerT - real
Time to Practice!!Time to Practice!!
Complete the remainder of the Ray Complete the remainder of the Ray Diagrams on your worksheetDiagrams on your worksheetIdentify the LOST for eachIdentify the LOST for eachComplete the “Discovery Stations” – taking Complete the “Discovery Stations” – taking down appropriate info and observations as down appropriate info and observations as you goyou go
Homework:Homework:Read text p.496-500Read text p.496-500Do Questions p. 501#1, 2, 5, 8a,bDo Questions p. 501#1, 2, 5, 8a,b
Worksheet Ray Diagrams #2Worksheet Ray Diagrams #2
L – in front (outside C)O – invertedS – largerT - real
Worksheet Ray Diagrams #3Worksheet Ray Diagrams #3
L – at CO – invertedS – sameT - real
Worksheet Ray Diagrams #4Worksheet Ray Diagrams #4
Ray 4 – strikes at V and angle i = angle r
L –O –S –T -… NO IMAGEReflective rays are parallel
Worksheet Ray Diagrams #5Worksheet Ray Diagrams #5
L – behind mirrorO – uprightS – largerT - virtual
Uses of concave mirrorsUses of concave mirrors
Satellite DishesSatellite Dishes
Solar cookersSolar cookers
Uses of concave mirrorsUses of concave mirrors
lasers, flashlights, car lasers, flashlights, car headlightsheadlights
Uses of concave mirrorsUses of concave mirrors
Radar detectorsRadar detectors – concave mirror in – concave mirror in shape (generator and detector are at focal shape (generator and detector are at focal point)point)
Uses of concave mirrorsUses of concave mirrors
TelescopesTelescopes
Sir Isaac Newton(1643–1727), developed one of the first reflector telescopes in 1668. Reflector telescopes are still used today, mainly in the field of astronomy.