Geometrical Optics

Chapter 24 + Other Tidbits

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On and on and on …

This is a short week. Schedule follows

So far, no room available for problem session. Still working on it.

Today we try to complete lenses. Quiz on Friday?

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November 2009SUNDAY MONDAY TUESDAY WEDNESDAY THURSDAY FRIDAY SATURDAY

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COMPLETE THINLENS

PROBLEMS SOLVING

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Interference& Diffraction

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THANKSGIVING

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THANKSGIVING

HOLIDAY

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Interference Diffraction

December 2009SUNDAY MONDAY TUESDAY WEDNESDAY THURSDAY FRIDAY SATURDAY

1REVIEW SESSIONIf Room isAvailable

NO ROOMAVAILAVLE

2EXAMINATIO

N #4

3 4INTERFERENCE&DIFFRACTION

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6 7OVERVIEW OFCOURSELAST DAY OF CLASS

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FINALEXAM

Most important case: converging lensObject to left of F1

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Most important case: converging lens

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Most important case: converging lens

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Most important case: converging lens

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Most important case: converging lens

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Aberrations are imperfections in the optical image formed by a

spherical lens (or optical mirror). There are five main aberrations:

1. Chromatic aberration. The refractive index of glass varies with wavelength. This results in different focal lengths and image magnifications for different colours.2. Spherical aberration. Lenses with spherical surfaces have a shorter focal length at their periphery than at their centre.3. Coma. The various circular zones of a lens produce an image of an off-axis point that is distorted radially into a comet shape known as a coma patch.4. Curvature of field. The focal surface is not a plane but a bowl shape.5. Astigmatism. Because a lens appears asymmetric to an off-axis beam, the image of a point is not a point but a short line radial from, or tangential to, the optic axis of the lens. These images are formed in different planes.6. Distortion. The image magnification is greater towards the edges of the field (pincushion distortion) or less (barrel distortion) than at its centre.

Remember the Spectrum?

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Dispersion

Index of refraction depends on the wavelength, or color.

f depends on the index of refraction.

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fRRn

111)1(

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Chromatic Aberration

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Example

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Correction : achromatic lens couple

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Spherical Aberration Results from the assumption of paraxial conditions. Real lenses need a wider opening, larger apertures.

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Spherical Aberration - Correcting

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Barrel Distortion

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Coma

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Some useful stuff

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Diaphram

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Intensity~Area

area double will 2by D Change

Fixed f stops will thereforego by factors of 2

Camera The intensity of the light striking the film or

CCD array is proportional to the area of the lens.

This is adjusted by the photographer by means of the aperture or diaphragm control.

f-number is defined by

Ex: A lens of focal length f=50mm and an aperture diameter of 25mm has an f number of 2, often written as “f/2”

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d

fnumberf

diameter aperture

length focal

f stops

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Multiplier sqrt(2) Designation

sqrt(2)^2 2.0 f/2

sqrt(2)^3 2.8 f/2.8

sqrt(2)^4 4.0 f/4

sqrt(2)^5 5.6 f/5.6

sqrt(2)^6 8.0 f/8

sqrt(2)^7 11.1 f/11

sqrt(2)^8 16.0 f/16

More on Camera

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The Microscope

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