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Unit 3: Light and Optical Instruments
J. PulickeelJanuary 2007
Lesson 4: Concave and Convex Reflections
Reflecting on Reflections
• Reflections occur when light rays bounce off objects.
• We can predict the direction in which reflected light rays travel by using the laws of reflection
1. The angle of reflection will ALWAYS equal the angle of incidence
2. The incident ray, the normal and the reflected ray are all in the same plane
YAY!!! MIRRORS!!!!
Mirror, Mirror on the Wall
Concave and Convex
• A Concave Mirror is a mirror that is curved inwards (like the mouth of a cave)
• The bowl of a spoon is concave
• Convex mirrors are mirrors that bulge outward like the surface of a shiny balloon
Concave and Convex
Concave Chaos
• A concave mirror can change the attitude of your image. The attitude describes if the image is upright or upside down
Concave Chaos
• A concave mirror can also make the
image appear larger or smaller
• It depends on where the image is relative to the concave surface
Concave Chaos
Centre of Curvature
Focal Point
Radius
½ Radius
Object behind the Centre
• If the object is behind the centre of curvature, it will appear upside down and smaller
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Object at the Centre
• If the object is at the centre of curvature, it will appear upside down but the same size
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Object in front of the Centre
• If the object is in front of the centre of curvature, it will appear upside down and larger
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Object in front of the Focal Point
• If the object is in front of the focal point, it will appear upright and larger
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Convex Mirrors
• Convex mirrors are more common than concave mirrors. They always produce smaller upright images.
• Because the image is smaller you can see more of the overall scene
Convex Mirrors
• A convex mirror is just the other side of a concave mirror!
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Concave Lenses
• A lens is a curved piece of transparent material .• A Concave lense is thinner and flatter in the
middle
• When light passes through the thicker more curved parts, it will bend more
A Convex lense is thicker and rounder in the middle
• This causes the refracting light rays to converge
In Summary
Regular Mirror All is good and happy and easy. Everyone loves a regular mirror
Concave Mirror
Image can be inverted (change in attitude) and the size can change
Convex Mirror More common than a concave mirror. Images appear upright and smaller. It is used on busses, in stores, etc…