American Society for Clinical Pathology (ASCP) Technologist in Cytogenetics certification (ASCP CG) Practice Test

The relationship between tube length and focal length can determine?

1. Brightness of the image

2. Resolution of the image

3. Magnification of the image

4. Color balance of the image

The correct answer is: Magnification of the image

The relationship between tube length and focal length is critical in determining the magnification of an optical system, such as a microscope. In microscopy, the tube length refers to the distance from the objective lens to the ocular lens, while the focal length is the distance from the lens to the point where light converges to form a sharp image. When the tube length is increased, the distance from the intermediate image formed by the objective to the ocular increases as well, which can effectively enhance the overall optical magnification of the system. This is because magnification is defined by the ratio of the image size to the object size, which depends on the focal lengths and the distances involved. Conversely, it's important to remember that while brightness, resolution, and color balance are impacted by various optical parameters and adjustments, they are not primarily determined by the relationship of tube length to focal length. Brightness is more influenced by light intensity and aperture, resolution is tied to the numerical aperture of the lens and the wavelength of light used, and color balance is related to the quality and type of lighting and filters used. Therefore, the most relevant aspect influenced by the tube length and focal length relationship is indeed the magnification of the image.