24. A collimated beam of light of diameter 2 mm is propagating along x-axis. The beam is required to be expanded in a collimated beam of diameter 14 mm using a system of two convex lenses. If first lens has focal length 40 mm, then the focal length of second lens is__________ mm.
(280):
Diameter of initial beam (before expansion), D=2 mm,
Diameter of final beam (after expansion), d = 14mm f_1 = 40 mm, f_2 = ?
We know that the ratio of final to initial beam diameter = ratio of focal length
M = Diameter of beam / D = 14/2 = 7
M = D_2/D_1 = f_2/ f_1 = 7
f_2 = 7 × 40 = 280 mm
(280):
Diameter of initial beam (before expansion), D=2 mm,
Diameter of final beam (after expansion), d = 14mm f_1 = 40 mm, f_2 = ?
We know that the ratio of final to initial beam diameter = ratio of focal length
M = Diameter of beam / D = 14/2 = 7
M = D_2/D_1 = f_2/ f_1 = 7
f_2 = 7 × 40 = 280 mm
(280):
Diameter of initial beam (before expansion), D=2 mm,
Diameter of final beam (after expansion), d = 14mm f_1 = 40 mm, f_2 = ?
We know that the ratio of final to initial beam diameter = ratio of focal length
M = Diameter of beam / D = 14/2 = 7
M = D_2/D_1 = f_2/ f_1 = 7
f_2 = 7 × 40 = 280 mm