Question 32
MediumOriginal questionWhat is the power of a convex lens of focal length 50 cm?
Show the answer and explanation
CorrectNot quiteAnswer C
Correct answer: C
Explanation
Power P = 1 ÷ f, with f in metres.
f = 50 cm = 0.5 m, so P = 1 ÷ 0.5 = +2 dioptre (D). A convex lens has positive power.
Worth noting
+0.02 D uses the focal length in centimetres; the dioptre needs metres.
- Concept
- Power of a lens
- Typical timeTypical
- 60 s
- Your timeYours
- —
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