Find the location and length of the final image

  • Thread starter Thread starter hraghav
  • Start date Start date
  • Tags Tags
    Image Length
Click For Summary
SUMMARY

The final image location produced by the lens is calculated to be di = -60.18504 cm, with a corresponding image length of 22.8682 cm. The calculations utilized the lens formula 1/f = 1/do + 1/di, where the focal length f is 22.7 cm and the object distance do is 24.7372 cm. The magnification was determined using both mirror and lens magnification formulas, resulting in a total magnification of M = 7.07996. The discussion highlights the importance of accurate ray diagrams and proper unit usage in optical calculations.

PREREQUISITES
  • Understanding of the lens formula (1/f = 1/do + 1/di)
  • Knowledge of magnification formulas for mirrors and lenses
  • Familiarity with optical concepts such as virtual and real images
  • Ability to create and interpret ray diagrams in optics
NEXT STEPS
  • Study the derivation and application of the lens formula in various optical systems
  • Learn about the significance of virtual versus real images in optics
  • Explore advanced ray diagram techniques for complex lens systems
  • Investigate the impact of significant figures and unit conversions in optical calculations
USEFUL FOR

Students and professionals in physics, particularly those focusing on optics, as well as educators seeking to enhance their understanding of lens and mirror calculations.

hraghav
Messages
48
Reaction score
5
Homework Statement
An object of length 3.23cm is located at the origin of a coordinate system. A concave reflecting surface is located at 30.5cmi^, and has a radius of 45.4cm. A converging lens of focal length 42cm is located at −83cmi^. This arrangement is shown in the diagram below. The light from the object that reflects off the mirror then refracts through the lens. The image from the mirror acts as an object for the lens, and the lens produces the final image. HINT: This question uses a coordinate system, but your lens and mirror formulas use scalar quantities with a set of rules. Use the coordinate system to convert and calculate the scalar quantities, then draw out the lens/mirror system and convert back into the coordinate system. The more accurate your drawing, the better your analysis will be. What is the location of the final image of the object as produced by the lens? What is the length of the final image of the object as produced by the lens? (A negative value means the image is inverted relative to the object orientation.)
Relevant Equations
1/f = 1/do + 1/di
Mm = -di/do
Ml = di/do
So I found the location of the image of the object produced by the mirror to be -58.2628 cmi^ and the length of the image of the object produced by the mirror to be -9.40012 cm. (these are correct values).

To find the location of the final image of the object as produced by the lens I used 1/f = 1/do + 1/di where
f = 45.4/2 = 22.7
do = 30.5
and found di = 88.7628
Then I added 30.5 - 88.7628 = -58.2628 (mirror image)
For object distance from lens: do = -58.2628 - (-83) = 24.7372
As Lens's focal length is 42 cm, using lens equation:
1 / 42 = 1 / 24.7372 + 1 /di
where di = -60.18504 as the final answer

For the length:
I used the mirror magnification formula ie Mm = -di/do = - 88.7628/ 30.5 = -2.91
Lens magnification formula ie Ml = di/do = -60.18504/ 24.7372 = -2.4329
total magnification is M = Mm * Ml
M = -2.91 * -2.4329 = 7.07996

Image length is 3.23 * 7.07996 = 22.8682

Both my answers are incorrect and I am not sure where I am making an error. Could someone please look at this and help me out?
Thank you!
 

Attachments

  • Screenshot 2024-07-19 at 2.58.40 PM.png
    Screenshot 2024-07-19 at 2.58.40 PM.png
    27.9 KB · Views: 62
Physics news on Phys.org
hraghav said:
The more accurate your drawing, the better your analysis will be.
You need a good ray diagram with distances and x-coordinates both marked. Without that, things can go horribly wrong!

hraghav said:
where di = -60.18504 as the final answer
Are you expected to convert this back to an x-coordinate? Maybe that's the problem.
(Also, units are missing and there are far too many significant figures.)

From my (distant) memories the negative sign here indicates that the image is virtual. In that case, the lens's image will be upright, not inverted - like a simple magnifying glass.
 
Thank you for your help I got both the answers :)
 
Last edited:
  • Like
Likes Steve4Physics

Similar threads

  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 11 ·
Replies
11
Views
1K
Replies
19
Views
960
Replies
4
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 16 ·
Replies
16
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 10 ·
Replies
10
Views
2K
  • · Replies 7 ·
Replies
7
Views
3K