However, if the object is at a distance slightly less
FIGURE 9 22 Plot of angle of deviation (d)
versus angle of incidence (i) for a
triangular prism Rationalised 2023-24
Ray Optics and
Optical Instruments
241
than the focal length of the lens, the image is virtual and closer than
infinity Although the closest comfortable distance for viewing the image
is when it is at the near point (distance D @ 25 cm), it causes some strain
on the eye