# Homework Help: Simple magnifier problem

1. Aug 4, 2007

### floridianfisher

1. The problem statement, all variables and given/known data

A boy scout starts a fire by using a lens from his eyeglasses to focus sunlight on kindling 5.2 cm from the lens. The boy scout has a near point of 15.2 cm. When the lens is used as a simple magnifier, give values for the following conditions. (Hint: Assume a "normal" eye.)
(a) What is the maximum magnification that can be achieved

(b) What is the magnification when the eye is relaxed

2. Relevant equations
1/p + 1/q = 1/f
Mmax= 1+ 25cm/f

3. The attempt at a solution
I used p=+5.2 and q= -(15.2)-((1/2)5.2)=-17.8
then 1/5.2 - 1/17.8 +1/f
f= 7.34
so, Mmax= 1+ 25/7.34= 4.406 but that is wrong?!?
can anyone help?

2. Aug 5, 2007

### chaoseverlasting

You have to put everything in meters... you're using cm... check your units...

3. Aug 5, 2007

### Staff: Mentor

That last equation assumes a near point of 25cm, but you are given a different near point to use.

(No problem using cm everywhere, as long as you are consistent.)

4. Aug 5, 2007

### floridianfisher

So i used the same equation except for Mmax I used 1+ 15.2/7.346= 3.068 but still the answere is not right?

5. Aug 5, 2007