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🔬Modern Optics

🔬modern optics review

14.1 Imaging with lenses and mirrors

2 min readLast Updated on July 22, 2024

Lenses and mirrors bend light to form images. This section covers how different optical elements create real or virtual images, and how to calculate image properties using equations like the thin lens formula.

Image formation isn't just about creating pictures. It's about understanding how light behaves, allowing us to design everything from eyeglasses to telescopes. We'll explore magnification, orientation, and the differences between real and virtual images.

Image Formation and Characteristics

Principles of image formation

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  • Light rays refract when passing through lenses or reflect off mirrors change direction based on the medium's refractive index (refraction) or bounce off surfaces at the same angle as the incident ray (reflection)
  • Converging lenses and concave mirrors focus light rays to form real images can be projected onto a screen
  • Diverging lenses and convex mirrors spread light rays forming virtual images cannot be projected onto a screen

Applications of lens and mirror equations

  • Thin lens equation 1f=1do+1di\frac{1}{f} = \frac{1}{d_o} + \frac{1}{d_i} relates focal length of the lens (ff), distance from object to lens (dod_o), and distance from lens to image (did_i)
  • Mirror equation 1f=1do+1di\frac{1}{f} = \frac{1}{d_o} + \frac{1}{d_i} uses focal length of the mirror (ff, positive for concave, negative for convex)
  • Magnification equation M=dido=hihoM = -\frac{d_i}{d_o} = \frac{h_i}{h_o} calculates magnification (MM) using image height (hih_i) and object height (hoh_o)

Real vs virtual images

  • Real images form when light rays converge can be projected onto a screen appear inverted relative to the object
  • Virtual images form when light rays diverge cannot be projected onto a screen appear upright relative to the object

Image Magnification and Orientation

Effects on image characteristics

  • Magnification depends on the ratio of image distance to object distance
    1. Larger image distance results in higher magnification
    2. Smaller object distance results in higher magnification
  • Converging lenses (convex) and concave mirrors can form both real and virtual images
    • Real images are inverted can be magnified (enlarged) or diminished (reduced in size)
    • Virtual images are upright always appear magnified
  • Diverging lenses (concave) and convex mirrors only form virtual, upright, diminished images
  • Orientation determined by image type
    • Real images appear inverted (upside-down)
    • Virtual images maintain upright orientation


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© 2025 Fiveable Inc. All rights reserved.
AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.