Why Was My Calculation of a -4.2 Diopter Lens's Focal Length Rejected?

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In summary, the problem asks for the focal length of a -4.2 diopter lens in meters. Using the formula -4.2 = 1/f, the focal length can be solved to be -0.2381 meters. However, online systems may be fussy about significant figures, so rounding the answer to 2 or 3 sig figs may be necessary for it to be accepted. If all attempts fail, the teacher can be consulted for assistance and the problem may still earn a point.
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sp1974
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The problem reads "What is the focal length (in meters) of a -4.2 diopter lens"



The formula equation I have is = 1/f to get the diopter power



-4.2 = 1/f and solve for f I get -.2381

This is a homework problem where the solutions are entered on line. I entered the solution above and it didn't accept. Any hints/help?
 
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  • #2
Looks right to me. But online systems are often fussy about things like significant figures: Try rounding it off to 2 sig figs. (Some systems insist on 3 sig figs.)
 
  • #3
Ok thanks. I know threwout the two semisters rounding has never been a factor but will try. Worst case if I use all my attempts I show teacher and get the 1 point for the problem. Thanks!
 

FAQ: Why Was My Calculation of a -4.2 Diopter Lens's Focal Length Rejected?

What is a -4.2 diopter lens?

A diopter is a unit of measurement used to determine the strength of a lens. A -4.2 diopter lens is a lens with a negative power of 4.2, which is used to correct for nearsightedness.

How do I solve a -4.2 diopter lens?

Solving a -4.2 diopter lens involves determining the correct prescription for the lens by measuring the curvature of the eye and determining the appropriate power needed to correct for the vision problem. This should be done by an optometrist or ophthalmologist.

What types of vision problems can a -4.2 diopter lens correct?

A -4.2 diopter lens is typically used to correct for moderate to severe nearsightedness. It can also be used to correct for astigmatism, which is a condition where the cornea is irregularly shaped, causing blurry vision.

Can a -4.2 diopter lens be used for all ages?

Yes, a -4.2 diopter lens can be used for people of all ages. However, it is more commonly prescribed for adults and older children as their eyes have stopped growing and changing.

How do I know if I need a -4.2 diopter lens?

If you have been experiencing difficulty seeing objects that are far away, it is possible that you may need a -4.2 diopter lens. The best way to know for sure is to visit an eye doctor for a comprehensive eye exam.

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