Two convex lenses f focal length 20 cm each are placed coaxially with a separation of 60 cm between them. find the image of a distance object formed by the combination by a. using thin les formula separately for the two lenses and b. using the equivalent lens. Note that although the combination forms a real image of as distance object on the other side, it is equivalent to as diverging lens as far as the locatiion of the final image is concerned.

Explanation

To solve the problem of finding the image formed by the combination of two convex lenses, we can approach it in two ways: using the thin lens formula separately for the two lenses and using the equivalent lens method.

### Part A: Using Thin Lens Formula Separately for the Two Lenses

1. **Identify the Given Data:**
- Focal length of each lens (f) = 20 cm
- Distance between the two lenses (d) = 60 cm
- For a distant object, we can assume the object distance (u) for the first lens is approximately infinity (u = -∞).
...