免费焦距计算器
根据透镜或反射镜参数计算焦距。
焦距
10.00 cm
Focal Length vs Object Distance
公式
## Focal Length The focal length defines the converging or diverging power of a lens or mirror. ### Formula **1/f = 1/d_o + 1/d_i** Lens power in diopters is **D = 1/f** (with f in meters). Positive focal length = converging lens; negative = diverging.
计算示例
An object at 30 cm produces an image at 15 cm.
- 011/f = 1/do + 1/di
- 021/f = 1/30 + 1/15
- 031/f = 0.0333 + 0.0667 = 0.1
- 04f = 10 cm
- 05Power = 100/10 = 10 diopters
常见问题
What are diopters?
The unit of lens power, equal to 1/f where f is in meters. Eyeglass prescriptions use diopters. Positive = farsighted correction; negative = nearsighted.
How does focal length relate to camera zoom?
Longer focal length gives higher magnification and a narrower field of view (telephoto). Shorter focal length gives a wider field of view (wide-angle).
What determines the focal length of a lens?
The curvature of the lens surfaces and the refractive index of the glass. The lensmaker's equation relates these to focal length.
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