The speed of wind is measured using the

1. Analyze the question The question asks which instrument is used to measure the speed of wind. Each option is a different instrument, so we need to match each one to what it measures.

2. Explain the concept Weather and ecology instruments each measure a specific factor:

• Wind vane: shows wind direction (it points into the wind).
• Anemometer: measures wind speed. It usually has rotating cups that spin faster when the wind is stronger.
• Photometer: measures light intensity.
• Barometer: measures atmospheric pressure.

3. Step-by-step solution

• Option A: a wind vane gives direction, not speed. ✗
• Option B: an anemometer measures wind speed. ✓
• Option C: a photometer measures light. ✗
• Option D: a barometer measures air pressure. ✗

4. Answer The correct option is B. anemometer.

5. Exam tip Link the names to their roots: anemos is Greek for "wind", so anemometer means "wind measurer". A barometer measures pressure (think "bar" as a unit of pressure), and a photometer measures light (think "photograph", which is light). A wind vane only points to the direction the wind blows from.