Question

an object 3.0cm high object is place 4.0cm in front of a converging lens with a focal length of 8.0cm. the object is located on the principal axis.

part 1. the image that will be formed will be . real, virtual or neither?

part 2. the image will be loacted on the same side of the lens at a distance of __ from the lens?

part 3. the magnification of the image will be ?

part 4. the size of the image (in cm) will be ?

Answer 1

Virtual Image Formation

Converging lenses form virtual images if the object distance is shorter than the focal length. Using the common form of the lens equation, i is negative. Such images are formed with the simple magnifier .

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The lens formula is as follows :

Where

• u is the object distance with proper sign convention.
• v is the image distance with proper sign convention.
• f is the focall length of the lens.

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In this problem :

• Ho= 3cm
• u=-4cm
• f=8cm

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We know that :

• Now, magnification for a lens is given by the following formula.

In this case :

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PART 1 : Since the image is formed on the same side as the object, the image is virtual.

It can also be seen from the ray diagram given above.

part 2. The image will be loacted on the same side of the lens at a distance of _8cm_ from the lens

Same side as the object because of the negative sign of v.

PART 3. The magnification of the image is 2 (as shown above)

PART 4 :The size of the image (in cm) will be 6cm

We know that :