Q2. Lenses and the Eye
An object O is positioned 3.5 m from a lens of focal
length f = -1.5 m as shown:
- Copy the diagram and draw in:
- the path of a parallel ray from the top of the object through
the lens;
- the path of a ray through the centre of the lens;
- and hence the location of the image.
- Calculate the image distance di from the
lens. Mark this distance on the diagram in a).
- A person with myopia wears such lenses to correct for their
vision of objects in the distance. The lenses are positioned 18 mm
from the eyes.
- What is the far point for the eyes?
- Find the focal length of the lens inside the eye
(fe) given that the distance between the lens
and the retina is 21.1 mm. (Assume that the eye lens can be
modelled as a thin convergent lens).