Optics focal length and optical power Question

• crystal1001
So the power is 1/4.03 m or 0.248 (0.25) and it is in diopters because the units of 1/f are in diopters. In summary, the focal length is 4.03 meters and the power is 0.25 diopters. The numbers are correct with the given 2 significant figures and the units are in meters and diopters respectively.

crystal1001

Homework Statement
What is the focal length and optical power (in diopters) of the lenses used to produce the following pairs of object and image distances?

do = 1.0 m
di = 0.33 m
Relevant Equations
focal length: 1/f = 1/do + 1/di
Power (diopters): 1/fD
1/f = 1/dₒ + 1/dᵢ = 1/1.0 + 1/0.33 = 4.03 m (focal length)

Power: 1/4.03 m or 0.248 (0.25)

*around to the2 decimal points? or leave it as a fraction?

((Did I do this correctly? I am not sure if this is correct and is it okay to be in meters not centimeters?))

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Delta2
Looks Ok to me! on this part. See next post by @ehild. Sorry.

The original numbers were 2 significant figures, so the answer should have the same, which you have. The same goes for the units, you matched what was given.

Last edited:
crystal1001 said:
do = 1.0 m
di = 0.33 m
Homework Equations: focal length: 1/f = 1/do + 1/di
Power (diopters): 1/fD

1/f = 1/dₒ + 1/dᵢ = 1/1.0 + 1/0.33 = 4.03 m (focal length)
The focal length is f, not 1/f. 1/f is the power (diopters) if f is measured in meters.

Tom.G

1. What is the difference between optics focal length and optical power?

The optics focal length refers to the distance between the lens and the point where parallel light rays converge to a single point. On the other hand, optical power is a measurement of the ability of a lens to bend light and is measured in diopters. In simple terms, focal length determines the magnification of an image, while optical power determines the strength of a lens.

2. How are optics focal length and optical power related?

Optics focal length and optical power are inversely related. This means that as the focal length increases, the optical power decreases, and vice versa. This relationship is important in understanding how different lenses can create different magnifications and strengths of images.

3. How is optics focal length measured?

Optics focal length is typically measured in millimeters using a lens or lens system. It is the distance from the center of the lens to the point where parallel light rays converge to a single point. This measurement can also be calculated using the thin lens equation, which takes into account the refractive index of the lens and the distance between the object and the lens.

4. What factors can affect optics focal length and optical power?

There are several factors that can affect optics focal length and optical power. These include the curvature and material of the lens, the distance between the object and the lens, and the wavelength of light. Additionally, the shape and placement of the lens in a lens system can also impact these measurements.

5. How are optics focal length and optical power used in real-life applications?

Optics focal length and optical power are essential in various fields, including astronomy, photography, and microscopy. In astronomy, they are used to determine the magnification and clarity of images captured by telescopes. In photography, they are used to create different perspectives and focus points in images. In microscopy, they are used to magnify and analyze small objects and materials. Additionally, these measurements are crucial in the design and manufacturing of lenses for eyeglasses and contact lenses.