Question

A 20 cm tall object is located 70 cm away from a diverging lens that has a focal length of 20 cm. Use a scaled ray tracing to answer parts a-d.
a. Is the image real or virtual?

b. Is the image upright or inverted?

c. How far from the lens is the image?

d. What is the height of the image?

e. Now use the thin lens equation to calculate the image distance and the magnification equation to determine the height of the image. Does this answer match your ray tracing?

Answer 1

Answer:

a) in divergent lenses all images are virtual , b) The right image, c) q = 28 cm  d)    h ’= 4.4 cm

Explanation:

For this exercise we will use the equation the constructor

        1 / f = 1 / p + 1 / q

Where f is the focal length, p the distance to object and q the distance to the image

      1 / q = 1 / f - 1 / p

As the lens is divergent the focal length is negative

      1 / q = 1 / (- 20) - 1/70

     1 / q = -0.05 - 0.014286 = 0.0643

      q = -15.56 cm

For a graphic analysis see attached

a) in divergent lenses all images are virtual

b) The right image

c) q = 28 cm

d) let's use the magnification equation

      M = h ’/ h = - q / p

      h ’= -q / p h

      h ’= - (-15.56) / 70 20

      h ’= 4.4 cm

Being positive indicates that the image is right