An insect 1.3 mm tall is placed 0.9 mm beyond the focal point of the objective l

Question

An insect 1.3 mm tall is placed 0.9 mm beyond the focal point of the objective lens of a compound microscope. The objective lens has a focal length of 11 mm , the eyepiece a focal length of 29 mm .

Part A

Where is the image formed by the objective lens?

Give your answer as the distance from the image to the lens. Express your answer using two significant figures.

s1 =____________________ mm

Part B

How tall is the image mentioned in part A?

Express your answer using two significant figures.

y1 = ______________________ mm

Part C

If you want to place the eyepiece so that the image it produces is at infinity, how far should this lens be from the image produced by the objective lens?

Express your answer using two significant figures.

d1 =_______________________ mm

Part D

Under the conditions of part C, find the overall magnification of the microscope.

Express your answer using two significant figures.

M=______________________

Explanation / Answer

A)

Thin lens equation is,

1/f=1/u+1/v

1/11 mm=1/11.9 mm +1/v

v=145 mm

b)

h'=(v/u)h

=(145 mm/11.9mm)1.3 mm

=16 mm

c)

Inorder to form the image at infinity, the distance between image by objective and eye piece must be equal to focal length of the eye piece.

Required distance is 29 mm

d)

M = -250L/(fo)(fe)

L = 145 - 11 = 134 mm

M = -250(134)/(11)(29)

M = -105

Negative sign indicates inverted image.

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