| 31. | The focal plane of the lantern is above the sea.
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| 32. | The focal plane of the lantern is above its base and above mean sea level.
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| 33. | Both have cell separation equal to cell focal length difference to maintain the focal plane.
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| 34. | The light's focal plane is above mean high water.
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| 35. | Illumination is via a diffuse source set at the focal plane of a collimating lens.
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| 36. | Placement of items behind the lens will alter the optics pathway, shifting the focal plane.
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| 37. | The object of measurement is usually located in the front focal plane of the lens.
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| 38. | The lightsource's focal plane is situated above sea level.
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| 39. | It changed the troublesome focal plane shutter for a leaf shutter in each C lens.
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| 40. | The tower is tall in all . from ground level to focal plane of the light.
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