1. What is Lens Focal Length?

Focal length is the distance between the center of a lens and its focal point. It determines the lens's magnifying power and field of view, making it a fundamental property in optics and photography.

2. How Does the Calculator Work?

The calculator uses the lens formula:

Where:

• \( FL \) — Focal length (m)
• \( d_o \) — Object distance from lens (m)
• \( d_i \) — Image distance from lens (m)

Explanation: This formula calculates the focal length of a lens based on the object distance and image distance, following the thin lens equation.

3. Importance of Focal Length Calculation

Details: Accurate focal length calculation is essential for designing optical systems, camera lenses, telescopes, microscopes, and understanding image formation in various optical devices.

4. Using the Calculator

Tips: Enter object distance and image distance in meters. Both values must be positive and greater than zero for valid calculations.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between focal length and focus distance?
A: Focal length is a fixed property of the lens, while focus distance is the adjustable distance between the lens and the subject to achieve sharp focus.

Q2: How does focal length affect field of view?
A: Shorter focal lengths provide wider fields of view, while longer focal lengths provide narrower, more magnified views.

Q3: Can this formula be used for both convex and concave lenses?
A: Yes, but remember that for concave lenses, the focal length is negative, and image distance may also be negative for virtual images.

Q4: What are typical focal length ranges for different lenses?
A: Wide-angle lenses: <35mm, Standard lenses: 35-70mm, Telephoto lenses: >70mm (in 35mm equivalent).

Q5: How does focal length relate to lens power?
A: Lens power (in diopters) is the reciprocal of focal length (in meters). A lens with 1 diopter power has a focal length of 1 meter.