Plane Mirror & Reflection
Normal – imaginary vertical line where the light strikes mirror
Angle of Incidence (θi) – the angle of the incident ray to the normal
Angle of Refection (θr) – the angle of the reflected ray to the normal.
Law of reflection – when light strikes a surface, θi = θr
Mirror(reflecting surface)
Reflecte
d RayIncident Ray
Normal
θrθi
LEFT- RIGHT REVERSAL
Da Vinci WritingMaterials: plane mirror, paper, pencil
Place the mirror on the paper and hold it there with your hand
While LOOKING into the mirror, try and print you name on the piece of paper so that it appears correctly IN THE MIRROR not on the page
You might need to practice.
Try it with your non-dominant hand
Try writing a secret message to a friend and have them de-code it
Check the accuracy of de-coding the message with the mirror
Specular ReflectionSpecular Reflection: reflection off of a
smooth, shiny surface. Reflected rays are all parallel to each other, and the image is clear.
Diffuse ReflectionDiffuse Reflection: reflection off of an irregular
or dull surface. Reflected rays are not parallel and the image is fuzzy.
←Specular
Diffuse ↓
DEMO!!Flash Light & Aluminum
Foil
Specular vs. Diffuse Specular vs. Diffuse ReflectionReflection
Applications of Specular and Diffuse Reflection:
•Countertop surfaces•Furniture or car wax•Glazed vs, unglazed ceramics•Matte vs. Glossy finish on photographs or in paint
Virtual ImageAn image formed by light coming from an
apparent light source; light is not coming from the actual image location
• Created using plane mirrors
Real ImageAn image that can be seen on a screen as a
result of light rays actually hitting (arriving) at the image location
Pig Demo
Describing an ImageWhen describing an image you need to
consider 4
characteristics known as SALT:
S= Size of image (compared to the object: same size, smaller or larger)
A= Attitude of image ( which way the image is oriented compared to the object: upright or inverted)
L= Location of image (infront or behind mirror or lens)
T= Type of image (real or virtual)
Size Attitude Location
Type
Image
Large Same Small
Upright or Inverted
In front or behind mirror
Virtual or real
An image in a plane mirror is always:
S= same size
A= Upright but backwards
L= Behind the mirror (same distance as object in front)
T= Virtual image
Creating an Image
How to find an Image?1. Draw the Plane mirror in correct location
2. Draw object on left side of the mirror
3. Draw a ray (incidence) through the object to the mirror and reflect the ray off the mirror
4. Change the angle and draw another ray through the object and reflect it off the mirror
5. Extend the Reflected rays “through” the mirror until the cross each other
6. Where the lines cross is where the object is located
Example 1 Simple
Creating Images
Locating Images in a Plane Mirror Lab
Purpose: to test the characteristics of an image in a plane mirror
Material: ray box paper plane mirror pencil ruler
Procedure: See Ms. Jamieson
Observations:
Locating Images in a Plane Mirror Lab
Arrow head (cm)
Arrow Tail (cm)
Length from Object to Mirror
Length from Image to mirror
Analysis:1.Using your observations describe (SALT) the image that appeared in the plane mirror?
2.What can you predict about all images in plane mirrors?
3.Is there a simpler way to locate the image in a plane mirror without using light rays?
Pla
ne
Mir
rors
Plane mirror worksheet
Applications of Plane Mirrors
1) Bathroom mirrors to see yourself
2) Rear View mirrors
3) Periscopes
Applications of Plane Mirrors
1) Cosmetic mirrors
2) Rear View mirrors
3) Periscopes
Can you write your name so it looks forward in the mirror?
Leonardo da Vinci used mirror writing when writing in his note book about his inventions. Can you write a mirror message to your neighbour?