Solutions: Medical Option - the EYE
An eye test shows that a person suffers from astigmatism.
(i) Give the main cause of astigmatism.
A non-spherical cornea
(ii) State the effect of astigmatism on the image seen.
When one plane is in focus, plane at 90° is out of focus
(iii) State the type of lens needed to correct this defect of vision.
A cylindrical (lens)
(iv) Give two quantities which must be known in order to manufacture the correcting lens.
The power of the lens
and the angle of correction
(Total 5 marks)