A thin plano-convex lens of index has a curved first surface with cm and a flat…
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 plano-convex lens of index nl=1.60 has a curved first surface with R1=+20 cm and a flat second surface (R2→∞) under convention CV1 (light left to right; R>0 when the centre of curvature lies to the right of the vertex; si>0 for a real image on the right). A printed letter is placed on the axis 25 cm to the left of the lens. Lens and letter are first in air (nm=1.00), then both submerged in water (nm=1.33) at the same separation. Assume a thin lens, paraxial rays and one wavelength; use 1/f=(nl/nm−1)(1/R1−1/R2).
((a)) Before calculating, predict whether the image stays on the same side of the lens, and whether the eye looking through the lens sees it further from the lens or nearer, once the lens is in water. Give the reason in one sentence.
((b)) Compute si in air.
((c)) Compute si in water.