# Lab 10: Lenses 1.Focal Length 2.Magnification 3.Lens Equation 4.Depth of Field 5.Spherical Aberrations and Curved Focal Plane 6.Chromatic Aberration 7.Astigmatism.

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Lab 10: Lenses 1.Focal Length 2.Magnification 3.Lens Equation 4.Depth of Field 5.Spherical Aberrations and Curved Focal Plane 6.Chromatic Aberration 7.Astigmatism (Optional) 8.Barrel and Pin Cushion Distortion (Optional) 9.Diverging Lenses

Lenses Lab Pay attention to quality of images in this lab –Photography needs good images on the film Do experiment #5 after all other experiments

Light Rays A source could be anywhere along the dashed line ????

Light Rays You locate the source by diverging rays!

Light Rays Observer: the converging point 1.makes diverging rays 2.appears to be the light source Converging point – image point Optical components

Light Rays Light rays from far away object appears to be...

Parallel Rays Nearly parallel! Huh?

Converging Lens Light rays deflect toward optical axis

Converging Lens Thick Thin A strong lens has a short focal length  Is it thicker or thinner?

Converging Lens optical axis parallel rays FF focal points focal length f parallel rays converge at F each lens has a unique f

Two Sides - Two Focal Points FF

Diverging Lens Light rays deflect away from optical axis

Diverging Lens Thick Thin A strong lens has a short focal length  Is it thicker or thinner?

Diverging Lens optical axis rays deflect away from optical axis

Diverging Lens F rays appear to come from point F F focal points focal length f

Ray Diagram Practice drawing ray diagrams for different lenses and object distances (o) in this lab

What is Ray Diagram? shows object (O), lens, and image (I) shows rays originating from an object using three easy rays, you can graphically determine image distance (i) and image size (L i )

Ray Diagram  1.Pick one point on object 2.Extend 3 rays in good direction

Ray Diagram  parallel center through F real image image (tip of arrow)

Image Quality  Out of focus No image Slightly out of focus Focused Sharp imageSmeared image

Ray Diagram  Object parallel through focal point center

Ray Diagram  Object Image (Virtual) rays appear to come from back of the lens

Expt 1: Focal Length Lens # 1 0 Screen Parallel light rays from far away light source Move lens until the image of light source appears on the screen

Magnification  Object How large? 10  larger or 0.5  larger? Magnification: ratio of image size to object size

Magnification  LoLo o LiLi i ray passing through center of lens How do you derive the magnification equation using the light ray passing through the center of the lens?

3. Lens Equation (Formula) f: focal length o: object distance i: image distance Lens equation relates f, o, and i real ( i > 0) inverted image or virtual ( i < 0) upright image  o i O I f > 0  o i O I f < 0

Light Unit Plastic ruler is on the light source! Inner circle diameter: 10 mm mm Face view

Expt 4: Depth of Focus (Field) Move screen Find the range (depth) of good focus Light Unit Lens # 2? Aperture Top view

Expt 5: Spherical Aberrations and Curved Focal Plane Screen Light Unit Peripheral MaskCentral Mask Move lightly Aperture Lens # 1 Aperture Examine image qualities Top view

Expt 6: Chromatic Aberration Roscolux Filters Adjust screen Compare the position of good focus #27 Medium Red #83 Medium Blue Light Unit Lens # 2? Aperture Top view http://www.rosco.com/images/filters/roscolux.jpg

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