The sun (diameter `d`) subtends an angle `theta` radian at the pole of a concave mirror of focal length `f`. What is the diameter of the image of the sun formed by the mirror ?

Explanation

To solve the problem of finding the diameter of the image of the sun formed by a concave mirror, we can follow these steps:

### Step 1: Understand the Geometry
The sun subtends an angle \( \theta \) at the pole of the concave mirror. This means that the rays from the sun, which is at a very large distance (essentially at infinity), will converge at the focal point of the mirror.

### Step 2: Identify the Focal Length
Given that the focal length of the concave mirror is \( f \), we can note that the image of the sun will form at the focal point of the mirror when the object (the sun) is at an infinite distance.

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