Spectacles, Focal length and Lens Formula

In summary, spectacles are a medical device used for improving vision and protecting the eyes. They consist of lenses and a frame. Focal length is the distance between the center of a lens and its focal point, and it is used to describe the strength of a lens. Focal length is measured in millimeters and can be found by measuring the distance between the center of the lens and the focal point or by using the lens formula. The lens formula is a mathematical equation that relates focal length, object distance, and image distance. It directly affects the strength of a lens in glasses, with a shorter focal length indicating a stronger lens and a longer focal length indicating a weaker lens. This formula is used to determine the necessary specifications for lenses in
  • #1
ZedCar
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1

Homework Statement



When using the lens formula: 1/f = 1/u + 1/v

for someone who has short sightedness and cannot focus on objects on objects more than 2.5m away, I get:

1/f = 1/infinity + 1/-2.5
f = -2.5 mIf using the formula for someone who had long sightedness and could not focus on objects closer than 2.5m does this mean the equation would be:

1/f = 1/infinity + 1/2.5
f = 2.5 m

Thanks! :smile:

Homework Equations



1/f = 1/u + 1/v

The Attempt at a Solution

 
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bumpity
 
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Anyone?
 

FAQ: Spectacles, Focal length and Lens Formula

What are spectacles?

Spectacles, also known as glasses, are a medical device used to improve vision or protect the eyes. They consist of lenses and a frame that holds the lenses in front of the eyes.

What is focal length?

Focal length is the distance between the center of a lens and its focal point. It is used to describe the strength or power of a lens in correcting vision. A shorter focal length indicates a stronger lens, while a longer focal length indicates a weaker lens.

How is focal length measured?

Focal length is measured in millimeters (mm) and can be found by measuring the distance between the center of the lens and the focal point. It can also be calculated using the lens formula, which takes into account the curvature of the lens and the refractive index of the material it is made of.

What is the lens formula?

The lens formula is a mathematical equation that relates the focal length (f), object distance (u), and image distance (v) of a lens. It is represented as 1/f = 1/u + 1/v. This formula is used to determine the necessary specifications for lenses in glasses and other optical devices.

How does the lens formula affect the strength of a lens in glasses?

The lens formula directly affects the strength of a lens in glasses. As the focal length decreases, the strength of the lens increases. This means that a lens with a shorter focal length will provide stronger magnification for nearsightedness, while a lens with a longer focal length will provide weaker magnification for farsightedness.

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