5. A meniscus lens with a refractive index of 1.490 has a centre thickness of 4.5mm, front radius of curvature +44.55 mm and back radius of curvature of +81.67 mm. Find the two surface powers and the back vertex power.

* i've found the answers for this question, F1= +11D, F2= -6D and Back vertex power Fv'= +5.38D

6. For problem 5, between what values can the centre thickness vary without introducing an error exceeding 0.12 D in the back vertex power?

7. For problem 5, what would be the error in back vertex power if thickness was ignored?

8. A lens in air has front surface power +6.00 D, back surface power 8.00 D, thickness 6.0 mm and refractive index 1.6. If the object is 0.25 m in front of the lens, where is the image located?

10. A prism has an angle of 10 degrees and power 9 D. What is the refractive index of the prism and what deviation would occur over a distance of 2 m

these are the answers: 6. 3.10mm to 5.87mm 7. -0.38D 8. (-)0.167mm in front of back surface 10. 1.514, 18cm