Register to reply 
Optics lenses question 
Share this thread: 
#1
Jul1913, 03:24 PM

P: 127

Hello,
If you have an object, and a biconvex lense, you are given the focal length, and you are given the magnification factor (M) to be 2, how are there two possibilities to place the object? One question I was doing asked this, and said: a) if the image is virtual, and M=2, find the distance. b) if the image is real, and M=2 find the distance. Basically, i found one answer easily, and noticed that the absolute value of the difference between my distance and the focal length, equaled the absolute value of the other distance and the focal length. So is this always the case? 


#2
Jul1913, 10:09 PM

Homework
Sci Advisor
HW Helper
Thanks
P: 12,974

The short answer is because there are two ways to get a magnified image from a converging lens.
To understand this  draw the ray diagrams. image height is 2units and object height is 1unit (M=2) put image and object some reasonable distance apart and draw the rays that must connect them ... and you'll find where the lens has to be and what the focal length is. Repeat for a virtual image. 


#3
Jul2013, 09:36 AM

P: 127

So would this be correct analytically? :
[C] If the distances between the vertical segments, and the focal length [C] are equal, then both will produce an image of the Same size, same distortion, except one will be real, and one will be virtual? 


Register to reply 
Related Discussions  
Optics of lenses and mirrors question:  General Physics  0  
What should be a very simple optics question is giving me problems (two lenses)  Classical Physics  2  
Question about optics and thin lenses  Introductory Physics Homework  1  
Question on Optics / Lenses  Engineering, Comp Sci, & Technology Homework  2  
Basic optics question  lenses  Introductory Physics Homework  1 