An optical instrument uses eye-lens of power 16 D and objective lens of power 50D and has a tube length of 16.25 cm. Name the optical instrument and calculate its magnifying power if forms the final image at infinity.

Explanation

To solve the problem step-by-step, we will first identify the optical instrument and then calculate its magnifying power.

### Step 1: Identify the Optical Instrument
The optical instrument described uses an objective lens and an eyepiece lens. Given that it has a high power for the objective lens (50 D) and a lower power for the eyepiece (16 D), and it forms the final image at infinity, we can conclude that this instrument is a **compound microscope**.

### Step 2: Calculate the Focal Lengths of the Lenses
The power (P) of a lens is related to its focal length (f) by the formula:
\[ P = \frac{1}{f} \]
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