A telescope has an objective of focal length 100 cm and an eye-piece of focal length 5 cm. What is the magnifying power of the telescope when it is in normal adjustment?

Options

A. 0.2
B. 2
C. 20
D. 200

Explanation

To find the magnifying power of a telescope in normal adjustment, we can use the formula:

### Step 1: Write down the formula for magnifying power (M)
The magnifying power (M) of a telescope in normal adjustment is given by the formula:
\[ M = \frac{f_o}{f_e} \]
where \( f_o \) is the focal length of the objective lens and \( f_e \) is the focal length of the eyepiece.

### Step 2: Identify the focal lengths
From the problem, we have:
- Focal length of the objective lens, \( f_o = 100 \, \text{cm} \)
- Focal length of the eyepiece, \( f_e = 5 \, \text{cm} \)

### Step 3: Substitute the values into the formula
Now, we substitute the values of \( f_o \) and \( f_e \) into the magnifying power formula:
\[ M = \frac{100 \, \text{cm}}{5 \, \text{cm}} \]

### Step 4: Calculate the magnifying power
Now, we perform the division:
\[ M = 20 \]

### Conclusion
The magnifying power of the telescope when it is in normal adjustment is \( M = 20 \).

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