Show that the factor `((1)/(R_(1))- (1)/(R_(2)))` (and therefore focal length) does not depend on which surface of the lens strike first.

Explanation

To show that the factor \(\left(\frac{1}{R_1} - \frac{1}{R_2}\right)\) (and therefore the focal length) does not depend on which surface of the lens the light strikes first, we can analyze the situation using the lens maker's formula.

### Step-by-Step Solution:

1. **Understanding the Lens Maker's Formula**:
The lens maker's formula is given by:
\[
\frac{1}{f} = \mu_{relative} \left(\frac{1}{R_1} - \frac{1}{R_2}\right)
...