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Transcript
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=q’ /q M=q’ /q=(h/f)/(h/N) = N/f 1/do = 1/f-(1/di )= 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 25-4 Telescopes …closest to eye. • M=q’ /q= fo /fe • See Example 25-6 • Reflecting telescopes use a large mirror instead of an objective lens. 25-4 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. • q= (1.22l)/D where D is diameter • See Example 25-8 p 776 HOMEWORK • P788 PR#1-3, 10,19-21, 28-30,38-39,44, 46-47 • Due Wednesday BOP • Test Chapter 24/25 on Thursday…(No Not Monday.) • Final Packets due April 29th