Question

Chapter 34, Problem 068 In the figure, a real inverted image 1 of an object dis formed by a certain lens not shown); the object-image separation is d = 39.2 cm, measured along the central axis of the lens. The image is just 1/2 the size of the object. (a) What kind of lens must be used to produce this image? (b) How far from the object must the lens be placed? (c) What is the focal length of the lens? Lens here (b) Number Units (c) Number Units

Answer 1

Solution)

A)

We know, image distance i=d-p

And, i/p=1/2

Where, p= object distance and d= object image separation=39.2 cm

So, p/2 =d-p

D=3p/2

So, p= 2d/3 =2*39.2/3=26.13 cm (Ans)

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B)

Focal length f= (1/i /+ 1/p)^-1

F= (1/d/3 + 1/2d/3)^-1 =(3/d + 3/2d)^-1 = (9/2d)^-1=(2d/9) = 2*39.2/9 =8.71 cm (Ans)

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Good luck!:)