### Author Topic: Hi! I've got a simple difficult problem...  (Read 8530 times)

#### razvan5050

• Newbie
• Posts: 3
##### Hi! I've got a simple difficult problem...
« on: October 09, 2011, 05:41:56 pm »
So I have to make the diagrams for the image attached. In total there should be 4 diagrams, representing every time the object moves. Now, I've done the first diagram, that was easy, but the others... I just can't get my head around them...

Any help would be appreciated.

Thank you!

#### Fu-Kwun Hwang

• Hero Member
• Posts: 3062
##### Re: Hi! I've got a simple difficult problem...
« Reply #1 on: October 09, 2011, 08:20:50 pm »
We would not be able to help if we do not know what is the problem.
Please write down the problem in detail.

#### razvan5050

• Newbie
• Posts: 3
##### Re: Hi! I've got a simple difficult problem...
« Reply #2 on: October 09, 2011, 08:27:02 pm »
I've simplified it a bit...

I just need to figure out where are the objects if they form the following virtual images and the rays that form them

#### lookang

• Hero Member
• Posts: 1774
• http://weelookang.blogspot.com
##### Re: Hi! I've got a simple difficult problem...
« Reply #3 on: October 09, 2011, 10:51:12 pm »
one assumption i made is the symbol is a diverging lens
http://budiprasetyoutomo.blogspot.com/2010/04/diverging-lens.html

if this assumption is valid, then
maybe u can explore this http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1155.0
and find out yourself.

picture 1 seems possible, u know where? appears to me to be at F on the right

pictue 2 seems to require the object to be an infinity on the right side

picture 3 i cant get it, is it a trick question?
« Last Edit: October 09, 2011, 10:53:11 pm by lookang »

#### razvan5050

• Newbie
• Posts: 3
##### Re: Hi! I've got a simple difficult problem...
« Reply #4 on: October 10, 2011, 05:45:21 pm »
First of all. The arrows I drew in the pictures are virtual objects, not virtual images, as I first said. Sorry!

Yes it's a diverging lens. I tried the same app and it just doesn't seem right. The thing is that the app doesn't know what happens when you move the object past the lens, when it becomes virtual. That's what I think. If you look at the red ray it goes to the left, when light only goes to the right...

It looks like a mirror image of the diagram when the object is placed in front of the lens. Just move the object back and forth and see. It's the exact mirror image.

Anyway this kind of ray diagrams are better drawn on paper. I just can't get it...