A camera-lens element is a thin biconvex lens (Chapter 1) made of BK7 crown glass…
PHYSICS · Subjective · Fermi University Physics · Optics & Photonics · Wave propagation and light in media · Wave propagation and light in media
Optics and Photonics, Ch Reflection and transmission at interfaces
Problem
A camera-lens element is a thin biconvex lens (Chapter 1) made of BK7 crown glass with refractive index n=1.52 at the design wavelength 589 nm and centre (axial) thickness t=4.50 mm. Take the bulk absorption coefficient of this glass at this wavelength as α=4.0×10−5 mm−1 (BK7 passes 99.9 per cent of the light through 25 mm), with the transmitted irradiance falling as I=I0e−αz over a path length z inside the glass. Light travels along the optical axis (normal incidence at both surfaces), and the two air-glass surfaces are to be treated as independent, each taking its own reflection loss, the only case this chapter computes. Find the overall fraction of the incident power that emerges from the far surface of the lens, including the reflection loss at each of the two surfaces and the bulk absorption over the centre thickness.