Principal Rays for Lenses Example

Question:
A converging lens has a focal length of 30 cm. Characterize the image formed by an object placed 45 cm from the lens.

Answer:

• From the ray tracing diagram above, we expect an enlarged, inverted, real image.
• The mirror equation yields:

  

• Positive value means real image!
• Magnification:

  m = -90/45 = -2

• Negative sign means image is inverted.

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