Mirror Magnification and Object-Image Separation
For a paraxial spherical mirror, transverse magnification is h_i/h_o = -v/u; its sign gives orientation and its magnitude gives size ratio.
Why this shows up in the exam
Estimating image size · Mirror-design calculations · Object-image separation problems
Learn the idea
Mirror magnification links image size to the ratio of signed image and object distances. The size and orientation of a mirror image reveal where it formed relative to the object.
🧠 Memory hook: Mirror magnification carries a minus: m = -v/u.
Get this one clearly and it pays off every single time it shows up in the paper. 🎯
Formulas & facts to keep ready
- m = h_i/h_o = -v/u — signed transverse magnification for a mirror
How to approach it
- 1Translate words into the sign of m
- 2Combine m = -v/u with the mirror formula
- 3Reconstruct positions before using separation
Common slip-ups that cost marks
- •Dropping the minus sign
- •Using separation as u + v without geometry
- •Treating negative magnification as negative size rather than inversion
🌟 That's the whole idea — you've got this. Try the practice set below; every question you attempt makes it stick a little harder.
Original chapter practice
Original questions for this chapter, not past-paper questions or an exact mapping to this individual concept.
A real object is placed 30 cm from a converging lens of focal length 10 cm. Find the real image distance.
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