Chapter 25 Optical Instruments 25-1 The Camera The basic parts of a camera are the light-tight box, lens, and shutter. Shutter speed refers to the speed of the shutter opening and closing. F-stop controls the amount of light coming into the light-tight box, by controlling the size of the opening F-stop=f/D

25-1 The Camera Circles of confusion involve objects not in focus forming circles of non-focused images…not all distances of objects can be in focus at one time. A smaller lens opening will cause there to be a wider range of in-focus object distances. See normal lens, telephoto lens, wide-angle lens, zoom lens. In a single-lens reflex system, you view through the actual lens… some cameras have a separate window. See Example 25-1

25-2 The Human Eye…Corrective Lenses See the eye pg. 761 Focusing of the eye involves accomodation… muscles contract to make the lens thicker for nearby objects and relax to make the lens thinner for far objects. The closest an eye can focus is the near point. The farthest an eye can focus is the far point. The normal eye has a npt of 25 cm and a fpt of infinity. See nearsightedness, farsightedness, and astigmatism on page 763 See Examples25-3 and 25-4 on p 764.

25-3 The Magnifying Glass Simple magnifier or magnifying glass. M=  ’  M=  ’  (h/f)/(h/N) = N/f  d o = 1/f-(1/d i )= 1/f + 1/N See page 767 for formulas and Example 25-6

25-4 Telescopes Several types of astronomical telescopes exist… Keplarian (refractive) Objective lens …closest to object…eyepiece …closest to eye. M=  ’  f o /f e   See Example 25-6 Reflecting telescopes use a large mirror instead of an objective lens Telescopes

Terrestrial telescopes provide upright images. Galilean and spyglass types. p770

25-5 Compound Microscopes See formulas page 771 See Example 25-7 p772

25-6 Aberrations of Lenses and Mirrors Spherical aberration Circle of least confusion. Coma and off-axis astigmatism Curvature of field Distortion- caused by variation of magnification at different distances. See p 773 Chromatic aberration Achromatic doublet

25-7 Limits of Resolution Resolution is the ability to discern between two separate points.  = (1.22 )/D where D is diameter See Example 25-8 p 776

HOMEWORK P788 PR#1-3, 10,19-21, 28-30,38-39,44, Due Wednesday BOP Test Chapter 24/25 on Thursday…(No Not Monday.) Final Packets due April 29th