optics lesson 3 introduction to reflection and plane mirrors
TRANSCRIPT
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Optics Lesson 3Introduction to Reflection and
Plane Mirrors
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Terminology of Reflection
• Perpendicular
• Parallel
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Terminology of Reflection
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Terminology of Reflection
• Plane Mirror (Flat Mirror)
• Concave Mirror (caved inwards)
• Convex Mirror (bumped out towards you)
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Reflection
The law of reflection – The angle of incidence is equal to the angle of reflection
Each arrow represents a “ray” of light.
Angle of Incidence
Angle of Reflection
Note: The angles are not measured to the edge They are measured to the “normal”
The normal is a doted line that is drawn perpendicular to the mirror.
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Reflection from a mirror
Incident ray
Normal
Reflected ray
Angle of incidence Angle of reflection
Mirror
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• The Law of ReflectionThe Law of Reflection
Angle of incidence = Angle of reflectionAngle of incidence = Angle of reflection
In other words, light gets reflected from a surface at the same angle it hits it.
The same !!!
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Types of Reflection
• Clear Reflection:– Reflection of light off a smooth surface
• Diffuse Reflection: – Reflection of light off an irregular survafe
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Clear vs. Diffuse Reflection
• Smooth, shiny surfaces have a clear reflection:
Rough, dull surfaces have a diffuse reflection.
Diffuse reflection is when light is scattered in different directions
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• Clear Reflection
• Diffuse Reflection
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Ray Diagrams
A ray diagram is a method used to determine where an image will appear when an object is viewed through a mirror or lens
A light ray radiates rays in millions of directions but we are only concerned with the ones that reach our eyes
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Locating an Image in a Mirror• Since we know light travels
in a straight line our brains think that the source is actually behind the mirror
• This is called a virtual because the image location we perceive is not real
• Note, dashed lines indicate light rays behind the mirror
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• We can use light rays and the laws of reflection to determine where our object is located and draw it. We do this using object-image lines
• Rules for object-image lines1)The distance between the object and mirror =
the distance between the mirror and image2)The object-image line is perpendicular to the
mirror surface
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• By choosing enough points we can accurately locate and draw our virtual image
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The Result - Lateral Inversion• The orientation of an image in a plane
mirror is flipped horizontally and in reverse order Try it for your self
L
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Lateral Inversion
Ambulance
- Why do you think they paint it backwards?
SCIENCE!
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SALT• When you describe the properties of an image,
you need to examine four characteristics
1)Size of image (compared to the object: same size, smaller, larger)
2)Attitude of image (which way the image is orientated compared to the object: upright or inverted)
3)Location of image (distance from mirror)
4)T ype of image (real or virtual)
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SALT
• An image in a plane mirror is ALWAYS the same size as the object, upright, equal distance behind the mirror virtual (behind the mirror)