Question

Using the thin lens equation, determine the location and size of each image of the "4" when it is a the 10cm mark, the 20cm convex lens(objective) is at the 80cm mark and the 10cm lens(eyepiece) is placed at the 114cm mark on the track. How many times larger is the final image when the eyepiece is at the 116cm mark?

Answer 1

Object '4' is at a distance from objective (first lens)

Focal length of objective

Thin lens formula: (Real positive sign convention)

First image is formed at a distance of to the right side of objective.

This serves as an object to eyepiece of focal length

Object distance from eyepiece is

Thin lens formula: (Real positive sign convention)

Final image is formed at a distance of to the left side of eyepiece.

Magnification of final image is

That is final image is formed at a distance of to the left side of eyepiece , size of image is same as size of object and is inverted .

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If eyepiece is at mark 116 cm.

First image is formed at a distance of to the right side of objective.

This serves as an object to eyepiece of focal length

Object distance from eyepiece is

Thin lens formula: (Real positive sign convention)

Final image is formed at a distance of to the left side of eyepiece.

Magnification of final image is

That is final image is formed at a distance of to the left side of eyepiece , size of image is double the size of object and is inverted .

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