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Plane Mirrors


laws of reflection


mirror rotation




Laws of Reflection



plane mirrors - laws of reflection



1. The incident ray, the reflected ray and the normal, at the point of incidence, all lie in the same plane.



the angle of incidence equals the angle of reflection



2. The angle of reflection equals the angle of incidence.

Hence an image can be located by taking two light rays from a point object and retracing them after reflection.



location of a virtual image from two reflected rays




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Plane Mirror Images


1. All images are virtual. That is, they cannot be projected on to a screen.


2. The image produced in a mirror is as far behind the mirror as the object is infront.


object distance = image distance



properties of a mirror image



3. The image is the same size as the object.


4. A line joining a point on the image to a corresponding point on the object is perpendicular to the mirror.


5. The image is laterally inverted (sideways upside down).



lateral inversion



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Mirror Rotation


When a light ray is normal to a mirror it reflects back the way it came.


However, if the mirror is tilted say, through θ o(theta) then the reflected light ray rotates through 2θ o .



deflection of a light ray by mirror rotation




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