Definition of focal length in English:

focal length

noun

1The distance between the centre of a lens or curved mirror and its focus.
Example sentencesExamples
- Telephoto lenses have focal lengths that range from about 85 mm (good for portraits) to supertelephotos' 300 mm to 600 mm or longer.
- That behavior is not affected by the medium in which the light travels, so the mirror's focal length would be no different in air or water.
- The shorter the focal length of the lens, the wider the field of vision.
- This will give a negative focal length for a convex lens of air inside water.
- Changing the lens's curvature changes the focal length, so that images at different distances appear in focus.
- A dioptre is 1 divided by the focal length of the lens in centimetres.
- The focal length of this lens can be varied somewhat without compromising the quality of the data.
- Our team chose two tube lenses with focal lengths that provided the necessary magnifications and fields of view.
- Long focal length lenses require less diffusion than short ones to achieve the same visual effect.
- When you increase the focal length of the lens (or decrease the film size) an apparent ‘compression’ of the image occurs.
- The focal length of a lens, for example, varies depending on the colour of light that is being focused.
- To overcome this, we must use a large number of mirror shells and as long a focal length as possible.
- I suggest that you look at any one that has a range in the focal length of the lens.
- A double convex lens with a focal length of 50 cm is fixed in a PVC pipe about 60 cm long.
- The focal length of the lens that you use, depends on where you are in relation to the fireworks and the composition you're looking for.
- Yet Stork determined the probable focal length of a concave mirror made by inverting and silvering the convex mirror shown in the painting.
- Varying the voltage across the lens, the researchers could change the focal length of the lens, because this alters its refractive index.
- Three things control how great the depth of field will be in a photograph: lens focal length, aperture, and distance from the subject.
- In 1647 Cavalieri published an important contribution to optics when he gave the relationship between the curvature of a thin lens and its focal length.
- This produces a rounded lens with a small focal length, so the drop can focus light only to a point near itself.
1. 1.1 The equivalent distance in a compound lens or telescope.
  Example sentencesExamples
  Huygens later went back to the study of optics and developed long focal length lenses used in ‘aerial telescopes.’
  The higher graze angle allows a shorter focal length and also preserves the collecting area of the telescope.
  One evening he was observing with a rather crude refractor (a lens telescope), with a focal length of 24 feet.
  The tube of the Gregorian telescope is thus shorter than the sum of the focal lengths of the two mirrors.
  By changing the distance between particular lenses, you can adjust the magnification power - the focal length - of the lens as a whole.
  He devised numerous ways of reducing the physical size of telescopes of long focal length, and machinery with which to move them.
  Small phase change leads to a long focal length, which is more suitable for telescope and satellite imaging applications.
  The magnification is simply the focal length of objective lens divided by the focal length of eyepiece.
  He developed a general rule for the focal length of lenses and described a reflecting telescope.

Definition of focal length in US English:

focal length

nounˈfoʊkəl ˌlɛŋθˈfōkəl ˌleNGTH

1The distance between the center of a lens or curved mirror and its focus.
Example sentencesExamples
- The focal length of a lens, for example, varies depending on the colour of light that is being focused.
- This produces a rounded lens with a small focal length, so the drop can focus light only to a point near itself.
- A dioptre is 1 divided by the focal length of the lens in centimetres.
- The focal length of this lens can be varied somewhat without compromising the quality of the data.
- Yet Stork determined the probable focal length of a concave mirror made by inverting and silvering the convex mirror shown in the painting.
- The focal length of the lens that you use, depends on where you are in relation to the fireworks and the composition you're looking for.
- To overcome this, we must use a large number of mirror shells and as long a focal length as possible.
- That behavior is not affected by the medium in which the light travels, so the mirror's focal length would be no different in air or water.
- In 1647 Cavalieri published an important contribution to optics when he gave the relationship between the curvature of a thin lens and its focal length.
- Three things control how great the depth of field will be in a photograph: lens focal length, aperture, and distance from the subject.
- A double convex lens with a focal length of 50 cm is fixed in a PVC pipe about 60 cm long.
- Telephoto lenses have focal lengths that range from about 85 mm (good for portraits) to supertelephotos' 300 mm to 600 mm or longer.
- Varying the voltage across the lens, the researchers could change the focal length of the lens, because this alters its refractive index.
- This will give a negative focal length for a convex lens of air inside water.
- Changing the lens's curvature changes the focal length, so that images at different distances appear in focus.
- Long focal length lenses require less diffusion than short ones to achieve the same visual effect.
- I suggest that you look at any one that has a range in the focal length of the lens.
- Our team chose two tube lenses with focal lengths that provided the necessary magnifications and fields of view.
- The shorter the focal length of the lens, the wider the field of vision.
- When you increase the focal length of the lens (or decrease the film size) an apparent ‘compression’ of the image occurs.
1. 1.1 The equivalent distance in a compound lens or telescope.
  Example sentencesExamples
  The higher graze angle allows a shorter focal length and also preserves the collecting area of the telescope.
  Small phase change leads to a long focal length, which is more suitable for telescope and satellite imaging applications.
  The tube of the Gregorian telescope is thus shorter than the sum of the focal lengths of the two mirrors.
  The magnification is simply the focal length of objective lens divided by the focal length of eyepiece.
  Huygens later went back to the study of optics and developed long focal length lenses used in ‘aerial telescopes.’
  One evening he was observing with a rather crude refractor (a lens telescope), with a focal length of 24 feet.
  He developed a general rule for the focal length of lenses and described a reflecting telescope.
  By changing the distance between particular lenses, you can adjust the magnification power - the focal length - of the lens as a whole.
  He devised numerous ways of reducing the physical size of telescopes of long focal length, and machinery with which to move them.

单词	focal length
释义	Definition of focal length in English: focal length noun 1The distance between the centre of a lens or curved mirror and its focus. Example sentencesExamples Telephoto lenses have focal lengths that range from about 85 mm (good for portraits) to supertelephotos' 300 mm to 600 mm or longer. That behavior is not affected by the medium in which the light travels, so the mirror's focal length would be no different in air or water. The shorter the focal length of the lens, the wider the field of vision. This will give a negative focal length for a convex lens of air inside water. Changing the lens's curvature changes the focal length, so that images at different distances appear in focus. A dioptre is 1 divided by the focal length of the lens in centimetres. The focal length of this lens can be varied somewhat without compromising the quality of the data. Our team chose two tube lenses with focal lengths that provided the necessary magnifications and fields of view. Long focal length lenses require less diffusion than short ones to achieve the same visual effect. When you increase the focal length of the lens (or decrease the film size) an apparent ‘compression’ of the image occurs. The focal length of a lens, for example, varies depending on the colour of light that is being focused. To overcome this, we must use a large number of mirror shells and as long a focal length as possible. I suggest that you look at any one that has a range in the focal length of the lens. A double convex lens with a focal length of 50 cm is fixed in a PVC pipe about 60 cm long. The focal length of the lens that you use, depends on where you are in relation to the fireworks and the composition you're looking for. Yet Stork determined the probable focal length of a concave mirror made by inverting and silvering the convex mirror shown in the painting. Varying the voltage across the lens, the researchers could change the focal length of the lens, because this alters its refractive index. Three things control how great the depth of field will be in a photograph: lens focal length, aperture, and distance from the subject. In 1647 Cavalieri published an important contribution to optics when he gave the relationship between the curvature of a thin lens and its focal length. This produces a rounded lens with a small focal length, so the drop can focus light only to a point near itself. 1.1 The equivalent distance in a compound lens or telescope. Example sentencesExamples Huygens later went back to the study of optics and developed long focal length lenses used in ‘aerial telescopes.’ The higher graze angle allows a shorter focal length and also preserves the collecting area of the telescope. One evening he was observing with a rather crude refractor (a lens telescope), with a focal length of 24 feet. The tube of the Gregorian telescope is thus shorter than the sum of the focal lengths of the two mirrors. By changing the distance between particular lenses, you can adjust the magnification power - the focal length - of the lens as a whole. He devised numerous ways of reducing the physical size of telescopes of long focal length, and machinery with which to move them. Small phase change leads to a long focal length, which is more suitable for telescope and satellite imaging applications. The magnification is simply the focal length of objective lens divided by the focal length of eyepiece. He developed a general rule for the focal length of lenses and described a reflecting telescope. Definition of focal length in US English: focal length nounˈfoʊkəl ˌlɛŋθˈfōkəl ˌleNGTH 1The distance between the center of a lens or curved mirror and its focus. Example sentencesExamples The focal length of a lens, for example, varies depending on the colour of light that is being focused. This produces a rounded lens with a small focal length, so the drop can focus light only to a point near itself. A dioptre is 1 divided by the focal length of the lens in centimetres. The focal length of this lens can be varied somewhat without compromising the quality of the data. Yet Stork determined the probable focal length of a concave mirror made by inverting and silvering the convex mirror shown in the painting. The focal length of the lens that you use, depends on where you are in relation to the fireworks and the composition you're looking for. To overcome this, we must use a large number of mirror shells and as long a focal length as possible. That behavior is not affected by the medium in which the light travels, so the mirror's focal length would be no different in air or water. In 1647 Cavalieri published an important contribution to optics when he gave the relationship between the curvature of a thin lens and its focal length. Three things control how great the depth of field will be in a photograph: lens focal length, aperture, and distance from the subject. A double convex lens with a focal length of 50 cm is fixed in a PVC pipe about 60 cm long. Telephoto lenses have focal lengths that range from about 85 mm (good for portraits) to supertelephotos' 300 mm to 600 mm or longer. Varying the voltage across the lens, the researchers could change the focal length of the lens, because this alters its refractive index. This will give a negative focal length for a convex lens of air inside water. Changing the lens's curvature changes the focal length, so that images at different distances appear in focus. Long focal length lenses require less diffusion than short ones to achieve the same visual effect. I suggest that you look at any one that has a range in the focal length of the lens. Our team chose two tube lenses with focal lengths that provided the necessary magnifications and fields of view. The shorter the focal length of the lens, the wider the field of vision. When you increase the focal length of the lens (or decrease the film size) an apparent ‘compression’ of the image occurs. 1.1 The equivalent distance in a compound lens or telescope. Example sentencesExamples The higher graze angle allows a shorter focal length and also preserves the collecting area of the telescope. Small phase change leads to a long focal length, which is more suitable for telescope and satellite imaging applications. The tube of the Gregorian telescope is thus shorter than the sum of the focal lengths of the two mirrors. The magnification is simply the focal length of objective lens divided by the focal length of eyepiece. Huygens later went back to the study of optics and developed long focal length lenses used in ‘aerial telescopes.’ One evening he was observing with a rather crude refractor (a lens telescope), with a focal length of 24 feet. He developed a general rule for the focal length of lenses and described a reflecting telescope. By changing the distance between particular lenses, you can adjust the magnification power - the focal length - of the lens as a whole. He devised numerous ways of reducing the physical size of telescopes of long focal length, and machinery with which to move them.
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