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 diagrams1. 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 M = magnificationdo = object distance Hi = image heightdi = image distance 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 M = magnificationdo = object distance Hi = image heightdi = image distance 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