A collimated beam of light of diameter 2 mm | vedclass

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Question

(B) For a beam expander consisting of two convex lenses, the magnification $M$ is given by the ratio of the diameters of the output beam and the input

Vedclass · Accepted Answer

$280$

Vedclass · Answer

(B) For a beam expander consisting of two convex lenses, the magnification $M$ is given by the ratio of the diameters of the output beam and the input beam, which is also equal to the ratio of the focal lengths of the two lenses:$M = \frac{D_{out}}{D_{in}} = \frac{f_2}{f_1}$Given:Input diameter $D_{in} = 2 \ mm$Output diameter $D_{out} = 14 \ mm$Focal length of the first lens $f_1 = 40 \ mm$Substituting the values into the formula:$\frac{14}{2} = \frac{f_2}{40}$$7 = \frac{f_2}{40}$$f_2 = 7 	imes 40 = 280 \ mm$Thus, the focal length of the second lens is $280 \ mm$.

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