Cue Column | Note Column
| Cue | Notes |
|---|---|
| Concave mirror | Converging; f < 0; R < 0 (Cartesian). Focus in front of mirror. Used: shaving mirror, solar concentrator, reflector telescope. |
| Convex mirror | Diverging; f > 0; R > 0 (Cartesian). Focus behind mirror. Used: rear-view mirror (wide field, erect image). |
| Mirror Formula | 1/v + 1/u = 1/f. All three distances measured from the pole P. |
| Object position | Always on the left (in front of the mirror). u is ALWAYS negative. |
| Real image | v < 0 (in front of mirror). Actual ray intersection. Can be projected. Always inverted for mirrors. |
| Virtual image | v > 0 (behind mirror). Extended ray intersection. Cannot be projected. Always erect for mirrors. |
| m = −v/u | Negative sign is MANDATORY for mirrors (unlike lenses). m < 0 → inverted. m > 0 → erect. |
| f = R/2 | Valid for both concave and convex mirrors. Both f and R carry the correct sign. |
| Concave mirror uses | Headlights (searchlights), shaving mirror (virtual erect magnified), solar furnace, ophthalmoscope. |
| Convex mirror uses | Rear-view mirror, security mirror, corner reflectors, ATM cameras. |
Summary
Spherical mirrors apply the same formula 1/v + 1/u = 1/f, but sign convention is everything. Concave mirror: both f and R are negative; convex: positive. The magnification m = −v/u for mirrors, with the minus sign being non-negotiable. The most common NEET error: using positive f for a concave mirror.