An optical setup on a bench is used to measure the image distance v v\,v from a thin convex lens to a screen where a sharp image of an illuminated object is focused.
The distance u u\,u between the illuminated object and the lens is held constant. A student obtains five repeat measurements for the image distance vvv: 28.3 cm,27.8 cm,28.9 cm,28.1 cm,27.5 cm28.3\text{ cm}, \quad 27.8\text{ cm}, \quad 28.9\text{ cm}, \quad 28.1\text{ cm}, \quad 27.5\text{ cm}28.3 cm,27.8 cm,28.9 cm,28.1 cm,27.5 cm
Calculate the absolute uncertainty in these measurements of vvv.