Home › Scottish National 5 › Physics › Mirrors and Lenses › A lens has a focal length of 12.5 cm. Using P eq…
A lens has a focal length of 12.5 cm. Using P equals 1 over f, what is its power?
A0.0800 D
B4.00 D
C8.00 D
D80.0 D
Answer & Solution
Correct answer: C. 8.00 D
1. Converting the focal length to metres gives f = 0.125 m.
2. Power is P = 1/f = 1 / 0.125 m.
3. Carrying out the division gives P = 8.00 D.
4. 0.0800 D mistakenly uses the focal length in metres as if it were already the power.
5. 80.0 D is ten times too large, from a misplaced decimal point in the division.
_Source: OpenStax Physics (CC BY 4.0), Ch 16 "Mirrors and Lenses", section 16.3 Lenses_
Related questions
In an eye where the lens-to-retina distance is fixed at 2.00 cm, an object sits 50.0 cm awA lens produces a 5.00 cm tall image of an 8.00 cm tall object when the object is placed 1A book page is held 6.50 cm from a concave lens whose focal length is -10.0 cm. Using d_i A light bulb sits 0.75 m from a convex lens with a 0.50 m focal length. Using d_i equals fSunlight is focused by a magnifying glass to a bright spot 8.00 cm from the lens. Using P The thin-lens equation used for lenses is the same equation used earlier for curved mirrorWhat kind of spectacle lens corrects farsightedness, and how does it help?What kind of spectacle lens corrects nearsightedness, and how does it help?