Final answer:
The power of a lens with a 10 cm focal length is 10 m⁻¹, or 10 diopters (D). The power formula is applied to the given focal length after converting it to meters.
Step-by-step explanation:
Understanding the Power of a Lens
When discussing the power of a lens, it is directly related to the lens's focal length. The formula to calculate the power (P) is P = 1/f, where f is the focal length in meters. For a lens with a focal length of 10 cm (which is 0.1 meters), the power of the lens is 10 m⁻¹, or 10 D (diopters). Therefore, the correct answer for a lens with a focal length of 10 cm would be 10 m⁻¹, or 10 D.
Similarly, for the practice problem of a lens with a 12.5 cm focal length, you would first convert the focal length to meters (0.125 meters) and then compute the power as P = 1/0.125, which calculates to 8 D. Regarding arc welding, the common shades of lens used are in the range of shade 8 to shade 12, depending on the specific welding process and amperage used.