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File Edit View History Bookmarks Tools Help X MasteringPhysics: ch 24 Hw x C Physics Forscientists And x G A15-cm-focal-length con... x Normally the magnication... x CA common optical Instru... x c Physics For scientists And x Maroon 5- one More Nig... x Q. Search https:// gphys /myct/i D-59145356 Physics for Scientists II Help l Close Ch 24 HW Problem 24.28 Resources previous l 7 of 10 next Problem 24.28 Part A A 15 cm-focal-length converging lens is 18 cm to the right of a For what value of Lis the final image of this two-lens system halfway between the two lenses? 7.0-cm-focal-length converging lens. A 1.8-cm-tall object is Express your answer to two significant figures and include the appropriate units. distance L to the left of the first lens. Value Units Submit My Answers Give Up Part B What is the height of the final image? Express your answer to two significant figures and include the appropriate units. h Value Units Submit My Answers Give Up Part C 8:46 PM Ask me anything 4/21/2016

Solution

a)

Halfway between the two lenses is 9 cm. So this puts the final image at -9 cm (virtual with respect to lens 2).

1/f₂ = 1/S₂ + 1/S₂\'

1/S₂\' = 1/15 - 1/(-9)

S₂\'=5.625 cm (Real Image)

The object for the second lens is 5.625 cm in front of the second lens. The object for the second lens and the image for the first lens is the same. This puts the image distance from the first lens at 13.2 cm

1/L =1/f -1/S₁\' = 1/7 - 1/13.2

L=14.9 cm

b)

Magnifiation

M=M₁M₂ = (-S₁\'/S₁)(-S₂\'/S₂) = (13.2/14.9)(-9/5.625)

M=-1.417

So the final image is

h^\'=-1.417 cm ,the image is inverted