Question 1 of 19
(demo test)
Product Demo for Ophthalmology Questions
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To make an effective Galilean telescope, what should be the power of the objective lens for this diagram?
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Clinical Optics
Telescopes and Optical Instruments
No
U
C
It is important to memorize the BASIC properties of the two different types of telescopes:
Galilean telescope:
- low plus power objective
- high negative power ocular
- lenses are separated by: 1/Pobjective - 1/Pocular (ignore positive or negative signs)
Astronomical (Keplerian) telescope:
- low plus power objective
- high plus power ocular
- lenses are separated by: 1/Pobjective + 1/Pocular
One way to remember this is that you Add the focal lengths for an Astronomical telescope to determine how far the lenses are separated from each other.
For this example:
distance between lenses = 1/Pobjective - 1/Pocular (ignore positive or negative signs)
10 cm = 1/Pobjective - 1/10
0.1 m = 1/Pobjective - 0.1
0.2 = 1/Pobjective
Pobjective = 1/0.2
Pobjective = 5 diopters
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