A thin symmetric biconvex lens of glass index has cm and cm under convention CV1…
PHYSICS · Multi-part · Fermi University Physics · Optics & Photonics · Geometrical optics and imaging · Geometrical optics and imaging
Optics and Photonics, Ch Image formation by mirrors and lenses
Problem
A thin symmetric biconvex lens of glass index nl=1.52 has R1=+15 cm and R2=−15 cm under convention CV1 (light left to right; R>0 when the centre of curvature lies to the right of the vertex; so>0 for a real object on the left, si>0 for a real image on the right). A small illuminated pinhole sits on the axis 60 cm to the left of the lens. The lens and the pinhole are first in air (nm=1.00) and are then both submerged in water (nm=1.33), the separation staying 60 cm. Assume a thin lens, paraxial rays and one wavelength; use 1/f=(nl/nm−1)(1/R1−1/R2).
((a)) Before calculating, predict in one sentence whether the image moves further from the lens or closer to it on submersion, and say why.
((b)) Compute si in air.
((c)) Compute si in water, and state whether the image is still real.