Calculating fD for a Diverging Lens: Is it Possible?

[NotMySubject!]

Homework Statement

Calculate a value for fD (the focal length of the diverging lens). Would this experiment be possible if fC > |fD|?

Homework Equations

Fcombo= (d_od_i)/(d_o+d_i)= (25*46)/(25+46) = 16.2 cm

1 - 1 = 1 fD= -24.83 cm
16.2 9.8 fD


Fcombo= (d_od_i)/(d_o+d_i)= (23*48)/(23+48) = 15.5 cm

1 - 1 = 1 fD= -26.69 cm
15.5 9.8 fD

The Attempt at a Solution

This experiment would not work if f_C > |f_D| because there would be no image produced on the screen, which would not be able to be measured to give us a d_i; we would be left with no way to calculate a F_combo or a f_D.
What is a better way to explain what happens? PLEASE HELP

 

[jbsteele]

If the focal length of the converging lens (fC) is greater than the absolute value of the focal length of the diverging lens (|fD|), then light passing through the two lenses would not be able to produce an image on the screen, since the diverging lens would not be able to counteract the convergence of light caused by the converging lens. As a result, the experiment would not be possible since it would be impossible to measure the distance between the object and the image to calculate the focal length of the combination of lenses.