MAGNIFIERS, MICROSCOPES AND TELESCOPES

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MAGNIFIERS, MICROSCOPESAND TELESCOPES
Dr. James Pierre Hauck J.P.H. PROFESSIONAL
SCIENCES, INC. JPHPS PMB 192, 2658 Del Mar
Heights Road Del Mar, CA 92014 858-566-8050 858-68
9-9353 FAX
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SIMPLE MAGNIFIER (converging lens)

• Principle is that it moves the nearpoint of the
  eye nearer by its focal length
• Adds focussing strength (diopters) to the eye
• Thus the approximate magnification is the ratio
  of the nearpoint to the focal length (i.e. it
  will be different for each user, and where they
  are located)
• Nominally the nearpoint is 250 mm, so the
  magnification will be
• Msm 250 mm/fo (the actual magnification will
  depend on the viewer)
• In principle a large amount of magnification is
  possible for a farsighted person with a short
  focal length magnifier, but in practice the
  magnification is limited
• Object distance is So lt fe and the image is
  virtual, upright at infinity

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MAGNIFICATION OF AN OBJECTIVE LENS
The objective lens magnifies an object by an
amount dependent on the position of the
object. The magnification is greater than 1 if
the object distance So lt 2 f . The
magnification goes to infinity as So -gt f
. Object distance So gt fo so image is inverted
and magnified.
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MAGNIFICATION OF A MICROSCOPE

• The microscope is essentially an objective which
  provides a magnified inverted image along with a
  simple magnifier that magnifies that image for
  the eye
• The microscope length is relatively fixed, so
  when a different objective lens is used, the
  object to objective lens distance is changed to
  relay the image to the same image plane Si L
  within the barrel of the microscope, changing the
  magnification by approximately the ratio of the
  focal lengths of the two objective lenses and
  Mo Si/So L/fo, ( So 1.05 to 1.2 fo
  fo )

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MAGNIFICATION OF A TELESCOPE

• The angular magnification of a telescope is a
  result of the objective lens which takes
  essentially parallel rays and make them converge
  to a focus at fo, and the magnification of the
  eyepiece Dn/fe resulting in
• MA -Si/So -fo/fe
• The eyepiece allows us to look at this image in
  the same way as in the simple magnifier and the
  eyepiece of the microscope
• Image is inverted, (may be re-inverted by a star
  diagonal along one axis)

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FOCUSSING THE MAGNIFIER, MICROSCOPE AND TELESCOPE

• For the simple magnifier, the eye and magnifier
  are moved such that the object is within the
  focal length from the lens, and the eye is moved
  away from the lens to increase the magnification
• (The magnification ranges from about 1 to 10x
  depending on the object distance, focal length of
  the lens, and the length of your arm, i.e. not a
  fixed value like the formula implies)
• For the microscope, the objective lens is moved
  toward the object for shorter focal lengths and
  higher magnification
• (The magnifcation ranges fromabout 10x to 1000x
• For the telescope, the eyepiece focal length