Optics Friday, March 6, 2015

Unit 8: EM Spectrum/Optics Friday, 3/6  Pick up a sheet of paper (do not write on it…it’s for later)  Respond to the following questions: 1. Using your prior knowledge of the Law of Reflection to predict what the angle of reflection will be if the angle of incidence is 15°. 2. If the same light wave moved from air through glass what would the angle of refraction be? Upcoming dates:  Monday, 3/9 – Spring break starts  Thursday, 3/19 – tentative date for EM Spectrum/Optics test  Thursday, 4/2 – 5SW extra credit due by 4:30  Friday, 4/10 – End of 5SW

Warm-up answer  Pick up a sheet of paper (do not write on it…it’s for later)  Respond to the following questions: 1. Using your prior knowledge of the Law of Reflection to predict what the angle of reflection will be if the angle of incidence is 15°. Draw a diagram to support your prediction. 2. If the same light wave moved from air through glass what would the angle of refraction be? Draw a diagram to support your prediction.

Quiz  Phones need to be in your bag or on my desk.  Take out your notes for the quiz.  You will have fifteen minutes to complete the quiz. When you are finished  Turn your quiz over  Find something quiet to do (no phones out) until everyone is done.

the change of direction of a ray of light as it passes obliquely from one medium into another of different transmission speed

When light travels from a less dense to more dense medium (light slows down), the ray is refracted toward the normal. Example: light slows down when it passes from air into water air water n i r i > r

When light travels from a more dense medium to a less dense medium (light speeds up), the ray is refracted away from the normal. Example: light speeds up when passing from glass into air air glass n i r i < r

An object’s ability to decrease the speed of light, and therefore cause refraction, is given by its index of refraction.

Guiding Questions What does the the law of reflection state? Include a diagram in your response? What is the function of the normal line?

Mirrors – Video Notes  Start video at 2:25 and end on 17:35  Note: you do not need a lab sheet just make your own observations of the students in the lab.

Introduction to lenses  On the back table you will find two different shaped lenses.  Place the lenses in front of the light source and observe what the light ray does.  You will trace the the incoming and outgoing (show me your rays before tracing).  Trace the rays on the paper provided (we will be adding notes to your diagrams.

Convex Lens

Concave Lens

Synthesizing what we know  For three minutes you will write about the how light rays behave (reflection and refraction) and what role the shape of lenses have on the direction of the outgoing light ray.

Ray Diagrams  Diagraming the light rays from an object allow us to predict the image we see.  Location of the image  Real or virtual  Orientation; erect or inverted  Size; enlarged, same size, reduced)  We will do this for convex lenses only!

Setting up the principal axis

Rules for Drawing Ray Diagrams Note: the point where the lines intersect is the image location. Darken in that point (point becomes the tip of the arrow)

Example 1

Example 2

Example 3

Example 4

Example 5