Thin Lens Equation

We started off Friday's class with Mr. Banow showing us how to derive the thin lens equation. Here is the link to the website: http://www.hirophysics.com/Anime/thinlenseq.html


The thin lens equation is:
1/di+1/do=1/f (which is exactly the same as the curved mirror equation)



M=hi/ho=-di/do

The sign rules are:
1. All distances are measured from the optical center
2. Distance of real images (behind the lens) are positive (virtual=negative)
3. Inverted=negative magnification, upright=positive

Examples:
1. A 8.0cm tall pencil is placed 17cm in front of a converging lens (with focal length of 10.0cm). How far and how tall will the image be?
ho=8.0cm
do=17cm
f=10.0cm
di=?
hi=?

1/di+1/do=1/f
1/di+1/17=1/10.0
1/di=1/10.0-1/17
di=24cm

hi/ho=-di/do
hi/8.0=-24/17
hi=-11cm

2. Where must a book be placed in front of a magnifying glass (converging, f=10.0cm), if a virtual image is to be formed 25cm in front of the lens? What is the magnification?
f=10.0cm
di=-25cm
do=?
M=?

1/di+1/do=1/f
1/-25+1/do=1/10.0
1/do=1/10.0-1/-25
do=7.1cm

M=-di/do
M=25/7.1
M=3.5x

http://www.youtube.com/watch?v=9pdEX4xtkLs

I don't know who is left to write the blog so whoever's last name comes first alphabetically of who is left can write it:)