[单选题]
A collimated laser beam emerging from a commercial He-Ne laser has a diameter of 1.0 mm. Twoconvex lenses are used to convert this beam to a well-collimated beam with 10.0 mm diameter. Thefirst lens has a focal length of 1.5 cm and is to be mounted at the output of the laser. What is thefocal length, f, of the second lens and how far from the first lens should it be placed?
A. A
B. B
C. C
D. D
E. E
参考答案: E
本题详细解析: Since there are two convex lenses, the set-up can be treated as a telescope. The lens
closest to the laser is the objective while the other is the eyepiece. This can then be
solved using :
$\frac{1}{f} = \frac{1}{d_a} + \frac{1}{d_t}$ and $M=\frac{f_{abj}}{f_eye}$
