Unit 6: Lenses and Mirrors
313 Fall 2015
Agenda 11/30/15
• Review Unit 5 Exam:
– Learning Target Check
• Begin Quarter 2 Project
Agenda 12/1/15
• Mirrors/Law of Reflection nSpire
– You may use your notes
• Review of Reflection
– Plane Mirrors and Curved Mirrors
• Science nSprired
– Concave mirrors
Plane Mirrors
• Remember:
– The image in a plane mirror is equally as far as the
object in front of the mirror.
– The incident ray of light reflects at the same angle
from the normal.
Plane Mirrors
• Images that are created by plane mirrors are
said to be “virtual”
• Virtual Image: an image appearing inside the
mirror. Considered an apparent divergence of
light, not an actual divergence of light.
Concave Mirrors
• If a plane mirror is curved inward, a Concave
mirror is the result.
Anatomy of a Concave Mirror
•
•
•
•
•
C: center of curvature (the center of the circular mirror)
A: vertex of the mirror
F: focal point (distance halfway between C and A)
R: radius (distance between C and A)
f: focal length (distance between F and A)
Focal Point of a Mirror
• The focal point is the point at which all light
parallel to the principal axis will converge.
Convex Mirror
• Imagine a plane mirror being bent the opposite
direction of a concave mirror.
• Notice the focal point is inside the mirror
Science nSpired
• You and your partner need a calculator and a
hat.
• You will work through the simulation.
• When you are done you may come and
observe the large concave mirror.
• It will be your goal to determine where the
focal length is on the large concave mirror.
Exit slip
1. What is the location in which all light
converges in a concave mirror?
2. If an object is outside the focal point, how
will the image be oriented? Right side up or
upside down?
3. If an object is inside the focal point, how will
the image be oriented?
4. What does an image look like if the object is
directly at the focal point?
Agenda 12/2/15
• Nspire: Concave vs. Convex Note Check
– 5 minutes to study the simulation
• Notes: Ray Diagrams for Concave/Convex Mirrors.
• Notes: Mirror Lens Equation
• HW: Curved Mirrors PS
Curved Mirrors
• You can memorize how the different images
will appear when placed at different locations
in front of a mirror, or you can learn ray
diagrams.
• Take notes on your handout
5 Steps to drawing ray diagrams
1. Draw a ray from the top of the object to the
mirror.
2. Draw a ray from the point on the mirror in step
one, through the focal point.
3. Extend this line behind the mirror.
4. Draw a ray connecting the focal point to the
mirror, passing through the top of the object.
5. This ray should reflect parallel to the principal
axis. Extend this line behind the mirror.
Wherever these two rays intersect is where the
image appears
Remember
• Virtual Image: images appearing behind the
mirror.
• Real Image: images being projected in front of
the mirror.
• Inverted: the image is upside down from the
object.
• Upright: the image is the same direction as the
object.
• The focal point is exactly ½ the distance
between the center of curvature and the vertex.
Mirror lens equation
• To determine the exact location either an
image, an object or a focal length, you must
use the mirror lens equation.
f = focal length
do = object distance
di = image distance
M = magnification
Hi = image height
Ho = object height
Example
• An object is placed 1.5 cm away from a
concave mirror and the image appears 2.0 cm
away from the mirror on the same side of the
mirror. What is the focal length?
Example
• An object is placed in front of a convex mirror
at a distance of 2.1cm. If the image appears
inside the mirror (virtual) at a distance of
1.1cm, what is the focal length of the mirror?
Example
• An object is placed in front of a convex mirror.
The object is 1.75m tall. If the image only
appears to be 1m tall, what is the level of
magnification?
Agenda 12/3/15
• Nspire: Mirror Lens Equation and Ray Diagrams
• Practice equations and ray diagrams
• Review for Quiz on Friday
Agenda 12/4
• Mirror Quiz
Agenda 12/8/15
• Doubles: Work Day for Quarter 2 Project
– Last work day
– Remember what you need to turn in!!
• 2nd and 3rd Hour: Intro to Lenses and Ray
Diagrams
– Quizzes back today
Rules for Drawing Ray Diagrams
(Lenses)
1. Draw a ray from the top of the object to the
middle of the lens.
2. Draw a ray from the point on the lens in step
one, through the focal point.
3. Extend this line behind the lens.
4. Draw a ray passing from the top of the object
through the vertex of the lens.
5. Extend this ray using a dashed line.
Wherever these two rays intersect is where the
image appears
Quick Tip
• If solid lines intersect: a real image appears
• If at least one dashed line intersects: a virtual
image appears
Agenda 12/9/15
• Nspire Quiz: Ray Diagram Lenses
• Convex Lens Lab
– Nspire Quiz Tomorrow on findings
• Mirror Lens Equation for Lenses
Mirror lens equation
• To determine the exact location either an
image, an object or a focal length, you must
use the mirror lens equation.
f = focal length
do = object distance
di = image distance
M = magnification
Hi = image height
Ho = object height
A few adjustments for lenses
• The object distance is always +.
• If the image or the focal point are on the
“real” side of the lens (Opposite the object)
their value is +.
• If the image or the focal point are on the
“virtual” side of the lens (same side as the
object) their value is -.
Example
• An object is placed at 20cm from a concave
lens. The focal point of this lens is 10cm.
Where will the image appear?
Example
• A 3.0cm object is placed at 15cm from a
convex lens with a focal point of 10cm. What
is the size of the image?
Agenda 12/14/15
• nSpire Lenses
• Review of Lenses and Mirrors
• Review for Test Tomorrow
• Review nSpire Quiz
• Rubric for Quarter II Project