In the figure below a converging lens is located at the origin. Ithas a focal le
ID: 1729225 • Letter: I
Question
In the figure below a converging lens is located at the origin. Ithas a focal length of f1= 20.5 cm. An object is placed a distance a= 25.5 cm to the left of the converging lens. In addition a concavemirror with focal length f2= 10.2 cm is located at L = 119.75 cm tothe right of the lens.The light from the object goes through the lens and then isreflected by the mirror. What is the position of the image producedby the mirror? Your answer should be measured relative to theorigin (the position of the converging lens), with a positivedistance to the right or a negative distance to the left. (Notethat we are not considering what happens when the light reflectedfrom the mirror goes back through the lens again!)
Calculate the height of the image produced by the mirror if theobject is 1.85 cm high.
Explanation / Answer
first the image by the lens S'= (1/F-1/S)^-1 = 104.55 cm to the left of the lens y'/y=-s'/s y'= -7.85 cm (-) means it isinverted and the image is real because it convergs --------- now the image by the mirror S2=119.75-104.55=15.2 S'2=(1/f2+1/S2)^-1= 31.008cm to the left of the mirror or (=119.75-31.008=88.742 cm to the right of the lens) Y'=-S'2*Y2/S2 notice thatY2=y' which we have already calculated Y'= 16.014 cm the image is real and erect