Calculating Angular Magnification: f=10cm, i=25cm

[rootX]

Homework Statement

f = 10 cm
i = 25 cm
Find angular magnification of lens

Homework Equations

Ang mag = theta_image/theta_object

The Attempt at a Solution

I found p to be 16.67
using 1/p+1/25=1/10

and I am not sure about the next step.
theta_0 = atan (16.67/25)
theta_f = atan (25/25)

and found thetas, and divided them to get 0.785/0.588=1.335 as my final answer.

 

[dynamicsolo]

Homework Equations

Ang mag = theta_image/theta_object

The Attempt at a Solution

I found p to be 16.67
using 1/p+1/25=1/10

I agree with your object distance...

and I am not sure about the next step.
theta_0 = atan (16.67/25)
theta_f = atan (25/25)

But the angular size of an object or image is the tangent of its linear size to its distance from the observer. (You don't want to take ratios of p/f and f/f.) You have no information about the object itself or the size of the image. I think you'll want to use the ratio

magnification M = -(image distance)/(object distance) .