The numerical value of the length of Galilean telescope for normal vision is (assuming `f_0` and `f_e` as positive length)

Options

A. `f_(0)xxf_(e)`
B. `(f_(0))/(f_(e))`
C. `f_(0)+f_(e)`
D. `f_(0)-f_(e)`

Explanation

To find the numerical value of the length of a Galilean telescope for normal vision, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Components of the Galilean Telescope**:
- A Galilean telescope consists of two lenses: a convex lens (the objective) and a concave lens (the eyepiece).
- The focal length of the objective lens is denoted as \( f_0 \) (positive value).
- The focal length of the eyepiece (concave lens) is denoted as \( f_e \) (considered negative in sign convention).

2. **Identify the Formula for Length**:
- The length \( L \) of the Galilean telescope is given by the difference between the focal lengths of the objective and the eyepiece:
\[ L = f_0 - f_e \]

3. **Substituting the Focal Lengths**:
- Since \( f_e \) is the focal length of a concave lens, it is negative. However, in this case, the problem states to consider \( f_e \) as a positive length.
- Therefore, we can rewrite the formula as:
\[ L = f_0 - (-f_e) = f_0 + f_e \]

4. **Conclusion**:
- The length of the Galilean telescope for normal vision, considering \( f_0 \) as positive and \( f_e \) as positive, is:
\[ L = f_0 + f_e \]

### Final Answer:
The numerical value of the length of the Galilean telescope for normal vision is \( L = f_0 + f_e \).