We can use the lens formula for this:
\[
\frac{1}{f} = \frac{1}{d_o} + \frac{1}{d_i}
\]
where \(f\) is the focal length, \(d_o\) is the object distance, and \(d_i\) is the image distance. Plugging in the given values, we get:
\[
\frac{1}{30} = \frac{1}{40} +
Show more…