1. ve = -25 cm
\(\frac{1}{u_e}=\frac{1}{v_e}-\frac{1}{f_e}\) = \(\frac{1}{-25}-\frac{1}{6.25}\)
∴ u0 = 5 cm
Length of the tube, L= |v0| + |ue|
∴ v0 = 15 – 5 = 10
\(\frac{1}{u_0}=\frac{1}{v_0}-\frac{1}{f_0}\) = \(\frac{1}{10}-\frac{1}{2}\)
ue = -2.5 cm.
2. ∴ v0 = 15 – fe = 15 – 6.25 = 8.75
\(\frac{1}{u_0}=\frac{1}{v_0}-\frac{1}{f_0}\)= \(\frac{1}{8.75}\) - \(\frac{1}{2}\)
u0 = -2.59 cm