Two lenses are mounted d= 25 cm apart on an optical bench. The focal length of t

Question

Two lenses are mounted d= 25 cm apart on an optical bench. The focal length of the first lens isf,-54 cm and that of the second lens isf2 lens 43 cm. An object of height ho-3.l cm is placed at a distance of do-28 cm in front of the first a) Ignoring the second lens for now, at what distance, in centimeters, behind the first lens is the object's image formed by that b) Calculate the magnification of that image, including its sign. c) Which choice best describes that image? d) Now consider the two-lens system and the final image it forms, ie., the image created by the second lens. What is the distance, in centimeters, between the object and its final image?

Explanation / Answer

a) Given that

do = 28 cm

f1 = 5.4 cm

di = ?

using lens equation

1/f = 1/do + 1/di

1/5.4 = (1/28)+(1/di)

di = 6.7 cm

b) magnification is m = -di/do = -6.7/28 = -0.24

c) real,dimished and inverted

d) now with second lens

object distance for second lens is do = 28-6.7 = 21.3 cm

f2 = 4.3 cm

using

1/f = (1/do ) + (1/di)

1/4.3 = (1/21.3)+(1/di)

di =5.4 cm

D = 28+25+5.4 = 58.4 cm

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