Physics with Trig II

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Physics with Trig II
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Where weve been

• Mechanics
• Solids Fluids
• Thermal Physics
• Sound
• Electricity
• Magnetism
• Induced Voltage
• ac Circuits
• Geometric Optics
• Wave Optics Interference

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Where were going

• Ch 25 Optical Instruments
• The Compound Microscope

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The Simple Magnifier
We need the angle, subtended by the object, at
the eye to be as large as possible. Near
Point Approx. 25 cm. Here, the object subtends
the largest possible angle for which (your)
unaided eye can focus sharply. A positive lens
(magnifier) helps the eye focus on an object
which is closer than your near point.
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The Simple Magnifier
Remember, an object place w/in the focal length
of a lens forms an upright, virtual, magnified
image.
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The Simple Magnifier
prime
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From Fig. 1A
If lens placed so object _at_ f Then, p f
From Fig. 1B
y is same for both angles
Near point for average person
So, by definition
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Now, for f 10 cm
So, a simple magnifier w/ f 10 cm forms image
whose height subtends an angle at the eye 2 ½
times as great as the angle subtended by the
object when viewed w/ unaided eye at near point.
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Figure 2
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From Figure 2
Ck. Sign from convention table
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More Fig. 2
Assumed
Angular Magnification
Lateral Magnification
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The Compound Microscope

• Object placed just outside focal point of
  objective lens.
• Forms a real, inverted image just inside focal
  point of ocular lens.

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The Compound Microscope
Now, Magnification
Your near point
Object for ocular lens
Approx. f2
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The Compound Microscope
f2
So,
Near point
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The Compound Microscope
So,
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The Compound Microscope
Now, an example
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The End