Ray Tracing for Convex Lens: How to Determine Image Distance and Realness

[toothpaste666]

Homework Statement

[/B]
B) Is the image real or virtual? Explain.
C) Using the lens equation, find the image distance.

2. Homework Equations
1/di + 1/do = 1/f

The Attempt at a Solution

A)

B) The image is real because it is on the opposite side of the lens as the source of light.

C) do = 6cm f = 3cm
1/do + 1/di = 1/f
1/di = 1/f - 1/do
1/di = do/f(do) - f/f(do)
1/di = (do-f)/(f*do)
di = (f*do)/(do-f) = (3cm * 6cm)/(6cm - 3cm) = (18cm^2)/(3cm) = 6cm
di = 6cm

 

[toothpaste666]

not too confident about my ray tracing. this is what it shows in the book but i know it differs depending on the situation

 

[ehild]

not too confident about my ray tracing. this is what it shows in the book but i know it differs depending on the situation

Your ray tracing is all right. The ray entering parallel with the axis goes through the focus on the other side of the lens.
The ray entering through the focus, goes parallel with the axis on the other side.

 

[toothpaste666]

ok i feel a little more confident that i got both of these problems right. thanks for the help

 

[ehild]

you are welcome.:)