(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

I have a concave lens where f < do < R. I have to provide a ray tracing diagram.

3. The attempt at a solution

I drew the focal ray through the focus and parallel to the principal axis. I drew the principal ray parallel to the principal axis then through the focus. I drew a dashed line from the center past the object tip and to the lens.

This leads to a diagram where there are no converging lines. However, if I arbitrarily choose some numbers to confirm this... this is where I get confused.

I'll choose a focal length (f) of 5cm. This means that R must be 2f. So, R = 10cm.

I'll choose an so between 5cm and 10cm of 7.5cm.

Given that:

1/so + 1/si = 1/f

1/0.075m + 1/si = 1/0.05m

si = 0.15m

M = -0.15m/0.075m = -2

This is telling me that I have a real image that is inverted and magnified by a factor of two.

Confused. Any help would be appreciated.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Concave Lens Ray Tracing

**Physics Forums | Science Articles, Homework Help, Discussion**