Question

5) a thick lens in air with P=5D, a=+2cm, and b=-5 is to be used to image an object that is 23cm from its front surface (first vertex). where does this image form relative to the back surface?

a. 65cm

b. 95cm

c. 100cm

d. 50cm

e. 153cm

Answer 1

Use the following equation to calculate the object vergence: U=100/u

Where u = object location in cm

U = object vergence = 100/-23 = -4.348D

Using the equation U + D = V Where

U = object vergence = -4.348D

D = lens power = +5.00D

V = refracting vergence of the image = –4.348D + (+5.00D) = +0.652D

Use the equation, v = image position = 100/V where V = +0.652D

v = image position = 100/+0.652 = +153 cm to the right of the lens.

Image is real

so, v = +153cm, so option e is the answer.