Q1.

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)