The coils of a heater sit 27.3 cm from a concave mirror that forms their image 3.00 m in front of it. What is the magnification?

1. Both distances must be in the same unit, so write the object distance as 27.3 cm = 0.273 m. 2. The magnification is m = minus di divided by do. 3. Substituting with units, m = minus (3.00 m) divided by (0.273 m). 4. Carrying out the division gives m = -11.0. 5. The negative sign means the image is inverted, which is expected since a real image from a converging mirror is always inverted. 6. The large size of the magnification is what helps spread the reflected heat energy over a wide area. 7. The +11.0 option drops the minus sign that the magnification equation carries, and would wrongly call the image upright. 8. The 0.0910 options invert the ratio, dividing the object distance by the image distance instead. _Source: OpenStax College Physics (CC BY 4.0), Ch 25 "Geometric Optics", section 25.7 Image Formation by Mirrors_