Question

A scientist uses a lens with a 17 cm focal length to focus light and create a holograph. The lens is 30 cm from the 25 cm tall image.
a. How far from the lens is the object?
b. What is the height of the object?
c. Describe the image characteristics: real/virtual, inverted/erect, larger/smaller than object.

Answer 1

Givens:
f= focal length= 17 cm
di= image position= 30 cm
hi= image height= 25 cm

Unknowns:
do= object position= ?
ho= object height== ? (I'm assuming that they are looking for the object hieght since they already gave the height of the image from the question)

a. How far from the lens is the object?
Use this formula to solve for do: \(\sf \Large \frac{1}{do} + \frac{1}{di} = \frac{1}{f}\)

b. What is the height of the image?
Use this formula to solve for ho: \(\sf \Large \frac{hi}{ho}= - \frac{di}{do}\)

**signs depends on the orientation of the image/object.