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Question : 7
Total: 7
An optical instrument uses an objective lens of power 100 D 40 D 20 cm
(a) Identify the optical instrument.
(b) Calculate the angular magnification produced by the instrument.
(a) Identify the optical instrument.
(b) Calculate the angular magnification produced by the instrument.
Solution:
(a) The instrument is called compound microscope because the focal length of objective lens is smaller than the focal length of eyepiece.
(b) Power of objective= P o = 100 D
∴ f o =
m = 1 cm
Power of eyepiece = P E = 40 D
∴ f E =
m = 2.5 cm
Power of eyepiece= P E = 40 D
∴ f E =
m = 2.5 cm
Length of tube= L = 20 cm
D = = 25 cm
Angular Magnification=
×
∴ =
×
= 200
(b) Power of objective
Power of eyepiece
Length of tube
Angular Magnification
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