Error in angular magnification calculation

[xamy]

Homework Statement

The wing of an insect is 1.7 mm long. When viewed through a microscope, the image is 1.4 m long and is located 5.9 m away. Determine the angular magnification.

Homework Equations

di/do=hi/ho
M=beta/alpha

alpha=object size/object distance

beta=image size/image distance

The Attempt at a Solution

di/do=hi/ho
5.9/do=1.4/0.0017
do=0.00716

alpha=0.0017/0.00716=0.237

beta=1.4/5.9=0.237
M=1
This answer is wrong. Can anyone please point out the mistake.

 

[haruspex]

di/do=hi/ho

This equation assumes the angular magnification is 1.
You need further information, e.g. the distance from the actual wing to... something. Go to http://en.wikipedia.org/wiki/Magnification#Magnification_as_a_number_.28optical_magnification.29 and search for "25".

 

[xamy]

This equation assumes the angular magnification is 1.
You need further information, e.g. the distance from the actual wing to... something. Go to http://en.wikipedia.org/wiki/Magnification#Magnification_as_a_number_.28optical_magnification.29 and search for "25".

I don't have angular magnification or focal length so I can't find the distance.

 

[haruspex]

I don't have angular magnification or focal length so I can't find the distance.

Did you find the reference to 25 at the link?

 

[xamy]

Did you find the reference to 25 at the link?

I have solved the question using 25cm for the distance. Thankyou for your guidance. Sorry earlier I was looking at the wrong portion of this link.

 

[haruspex]

I have solved the question using 25cm for the distance. Thankyou for your guidance. Sorry earlier I was looking at the wrong portion of this link.

Ok, good.