Physics Oct.24, 2014 Open to 5.2 Can you see the buck? (not the doe)

Uses of Mirrors & Lenses What are some commercial uses of lenses? Glasses/ Contacts Projectors Cameras Microscopes Telescopes Binoculars*

Camera

Telescope Clip

Binoculars

Projector show HOLT CD animations

Microscope Linked to HOLT CD animations Clip

Mirrors & Lenses Convex Concave

Mirascope

Mirrors & Lenses Converging – light rays come together Diverging – light rays spread out

Types of Images Virtual Image Real Image right-side-up cannot be projected on a screen Real Image upside-down can be displayed on a screen*

Image formation Distance affects the angle of view Far away- small angle of view allows very little detail to be seen Closer- larger angle of view creates more details to be seen

Ray Diagram Setup Principal axis- line in a lens that joins the centers of curvature of the lens surface

Ray Diagram Setup Focal point- point at which a beam of parallel light, to the principal axis, converges

Ray Diagram Setup Focal Plane- all possible points on a plane for the location of the focal point

Ray Diagram Setup Focal length- distance between center of lens and its focal point

Ray Diagrams: Copy the instructions on the next few slides and then we will look at the rules in a virtual “draw”.

How to draw a mirror ray diagram: parallel to the axis then go through the focal point. to the center of the mirror then out at the same angle.*

Let’s draw a correct ray diagram The scope of vision looks like this in yellow. The first blue ray goes from the top of the object – parallel to the “principal axis” and comes back at the same angle (90) P Start with a plane mirror. The lines represent the back of the mirror. We need an object to reflect. Faces are hard to draw. Let’s draw the letter P. Let’s trace the light rays that will produce an image of the letter P. When we draw light rays we are creating a ray diagram. In other words a diagram that maps out the rays. We will pick rays that are helpful in locating specific spots of an object. We’ll draw two rays to help locate the top left corner of the letter P. There are many more rays we could draw, but two are enough. So we’ll keep it simple. The first ray we’ll draw (blue) will go straight to the mirror and bounces back at the same angle. The second ray we’ll draw (red) will go to the mirror at an angle and bounce off at the same angle. These rays do not intersect so we will need to artificially add some rays that will intersect so we will know where to put the upper left corner of the P’s image.

Let’s draw a correct ray diagram There is no focal point on a flat mirror. If we are wanting to begin at the top of the ‘P’ - the angle is whatever you choose with the red arrow P Start with a plane mirror. The lines represent the back of the mirror. We need an object to reflect. Faces are hard to draw. Let’s draw the letter P. Let’s trace the light rays that will produce an image of the letter P. When we draw light rays we are creating a ray diagram. In other words a diagram that maps out the rays. We will pick rays that are helpful in locating specific spots of an object. We’ll draw two rays to help locate the top left corner of the letter P. There are many more rays we could draw, but two are enough. So we’ll keep it simple. The first ray we’ll draw (blue) will go straight to the mirror and bounces back at the same angle. The second ray we’ll draw (red) will go to the mirror at an angle and bounce off at the same angle. These rays do not intersect so we will need to artificially add some rays that will intersect so we will know where to put the upper left corner of the P’s image.

http://www. regentsprep. org/Regents/physics/phys09/bcraytrace/default http://www.regentsprep.org/Regents/physics/phys09/bcraytrace/default.htm

How to draw a lens ray diagram: parallel to the axis then to through the focal point. straight through the center of lens. *

http://www. regentsprep. org/Regents/physics/phys09/bcraytrace/default http://www.regentsprep.org/Regents/physics/phys09/bcraytrace/default.htm

Let’s draw a correct ray diagram P Virtual rays are drawn behind the mirror. Real light rays do not go behind the mirror. We will draw dotted lines to represent these virtual rays. Ray 1 (dotted blue): trace the reflected blue ray straight back Ray 2 (dotted red): trace the reflected red ray straight back The point of intersection is where the upper left corner of the P will be seen.

Let’s draw a correct ray diagram P P Repeat for the bottom right corner. Then draw in the image placing the appropriate parts at the intersections. This image is virtual because we used the “imaginary” lines. We did not use the real rays. This image can NOT be projected on a screen. The

More practice

More practice

Mirror & Lens Equation distance to image Focal length distance to object

Mirrors and Lenses have many opposite properties. For a mirror: the positive side is the side the object is on. To remember this, I think "light should reflect off a mirror therefore making that side positive." For a lens: the object is on the negative side. To remember this, I think, "light should go through a lens therefore making it the positive side." The exception, even though the object is on the negative side, it has a positive distance.

Example) Mr. Nelson is showing slides to his physics class, if the slides are positioned 15.5 cm from the projector lens that has a focal length of 15.0 cm, where should the screen be placed to produce the clearest image of the slide? do = 15.5 cm f = 15.0 cm di = ?

Power of Eyeglasses Power – measured in diopters (1/meter) focal length (m)*

Example) Beth is farsighted, so she must wear glasses to see objects close by. If her glasses have a focal length of 0.30 m, what is their power in diopters? P = ? f = .30 m

Image Size Magnification- image is observed through a wider angle with the use of a lens image height* Magnification object height*

Practice Problem As you look through your binoculars at a deer out in the field, the deer appears to be 3 m tall but the deer in real life is only 1 m tall. How much magnification do your binoculars have?

As you look through your binoculars at a deer out in the field, the deer appears to be 3 m tall but the deer in real life is only 1 m tall. How much magnification do your binoculars have?

Mirror and Lens Overview

Lemony Snickets Clip

Talking on a LASER Demo

http://www.andrews.edu/phys/wiki/PhysLab/doku.php?id=lab10 lab

Homework 29s – Review Worksheet Due – Nov. 8th Worksheets you should have complete: We will be in the auditorium the next 2 LG’s Physics Great America – May 19th $50-$55 Start saving now if you plan on going Need to have a C or better 12s 23s 13s 24s 14s 28s 15s

Demonstration on how to print multiple PowerPoint slides on 1 page…