Focal Length of Lens: Object 5 cm Tall, 10 cm Away

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SUMMARY

The discussion centers on calculating the focal length of a concave lens given an object height of 5 cm and an object distance of 10 cm, resulting in an image that is one-fifth the size of the object. The lens equation, which relates object distance (u), image distance (v), and focal length (f), is essential for solving this problem. The formula is 1/f = 1/v + 1/u. Participants emphasize the importance of understanding the lens equation and visualizing the scenario through sketches to clarify the relationships between the object, image, and lens.

PREREQUISITES
  • Understanding of the lens equation (1/f = 1/v + 1/u)
  • Knowledge of concave lens properties
  • Familiarity with image formation concepts in optics
  • Ability to interpret and create ray diagrams
NEXT STEPS
  • Study the derivation and applications of the lens equation
  • Learn how to draw ray diagrams for concave lenses
  • Explore the characteristics of virtual images produced by concave lenses
  • Practice problems involving different object distances and image sizes
USEFUL FOR

Students studying optics, physics educators, and anyone seeking to understand lens behavior and image formation principles.

dev-hud
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An object 5 cm tall is 10 cm from a convace lens. The resulting image is one fifth as large as the object. What is the focal length of the lens?

I have been doing questions involving focal lenght, but not when the resulting image is a fraction of the original image. i do not know where to start or what equation(s) to use?? :(
 
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dev-hud said:
An object 5 cm tall is 10 cm from a convace lens. The resulting image is one fifth as large as the object. What is the focal length of the lens?

I have been doing questions involving focal lenght, but not when the resulting image is a fraction of the original image. i do not know where to start or what equation(s) to use?? :(

Use the lens equation. Can you show us what that is? And make a sketch. Could you show us a sketch of the situation?
 

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