A letter "F" is produced by several LED lights on an object surface. The light from this object then reflects off a concave/converging Mirror and reaches a Screen (Image) located 100 cm away from the Mirror. Slide the Object back and forth along the optical axis to attempt to form a focused image on the Screen. Use a ruler to measure the heights of the object and focused image.
Mirror Focal Length = 25cm
When you have an Image formed that you want to measure the height of, use a ruler to measure the heights of the object and image.
Measure from the bottom most point of the image to the top most point of the image. If you measure this upward, the image has positive (+) orientation, if you measure this downward (i.e. the "bottom" of the image is at the top of the screen and the "top" of the image is at the bottom fo the screen), the image has negative (-) orientation.