0
$\begingroup$

enter image description here Hey. I got this question wrong and I don’t get the explanation. I know that to fix myopia you need a concave lens to diverge the light rays so that the eye lens converges them further back on the retina. I don’t understand why the answer says that overall focal length decreases. If the image focuses further back wouldn’t that mean the focal length has increased? And I know that concave lenses have negative powers but the explanation says adding a corrective lens increases the overall power. Shouldn’t adding a concave lens with a negative power decrease the overall power of the system? If someone could clear these up for me I would really appreciate it.

$\endgroup$
0
$\begingroup$

The explanation is wrong, and you are right. Adding the concave lens decreases the convergence power and (as is evident from the figure) increases the overall focal length. The correct answer would be C.

$\endgroup$
  • $\begingroup$ Awesome. Thanks for giving me assurance. $\endgroup$ – user17763 Aug 7 at 14:16

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.