Chromatic aberrations in objectives Questions

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1. Which of the following is an example of defects of aberrations in objectives?

  • a) Curvature of the field, astigmatism
  • b) Chromatic and spherical aberrations
  • c) Distortion, lateral color, coma
  • d) All of the above

2. Which of the following is incorrect for spherical aberrations?

  • a) Spherical aberrations arise due to greater power in the inner portion of spherical surface than outer portion
  • b) It can be corrected by combinations of convergent and divergent lens elements
  • c) It causes some of the light to diffuse out into the ring structure from the central spot
  • d) It causes loss of contrast in normal microscope preparation

3. In which kind of aberrations cushion shape and barrel shape alterations are found to appear?

  • a) Curvature of field
  • b) Astigmatism
  • c) Distortion
  • d) Spherical aberration

4. What is the correct reason for curvature of the field?

  • a) Greater power in the outer portion of the spherical surface than in the inner portion
  • b) Lens surface having different magnifications at the marginal and the central portion of the
    image
  • c) Marginal portion of the image come to focus at a different distance from those of central
    portion of the image
  • d) All of the above

5. _______ in the center of the field is an indication of damage to the objective:

  • a) Lateral color
  • b) Coma
  • c) Stigma
  • d) All of the above

6. Due to dispersive power of the lens, shortest waves refracted _ and longest waves
refracted __
:

  • a) Less, most
  • b) Most, less
  • c) Less, less
  • d) Most, most

7. color rays cross the lens axis first and _ color rays cross the lens axis last:

  • a) Blue-violet, red
  • b) Red, yellow-green
  • c) Green, yellow
  • d) Red, indigo

8. Formation of halos is a characteristic of __ aberration:

  • a) Spherical
  • b) Lateral color
  • c) Distortion
  • d) Chromatic

9. How chromatic aberration can be eliminated?

  • a) Reducing the aperture of lens
  • b) Using a lens composed of more than one material
  • c) Both of the above
  • d) Use of prism lens

10. If two optical glasses are selected to image light of two different wavelength at the same focal point, the lens is said to be _____

  • a) Apochromatic
  • b) Achromatic
  • c) Semi-apochromatic
  • d) Fluorite

11. ________ objective is a lens system that is corrected for light of three different wavelengths:

  • a) Apochromatic
  • b) Achromatic
  • c) Semi-apochromatic
  • d) All of the above

12. Semi-apochromatic and apochromatic objectives are composed of________ mineral in
combination with lenses of optical glasses:

  • a) Fluoride
  • b) Fluorite
  • c) Any halide
  • d) None of the above

13. Faint blue or yellow color is exhibited through _______ objective:

  • a) Apochromatic
  • b) Achromatic
  • c) Semi-apochromatic
  • d) All of the above

14. Due to shifting of focus faint green and pink color halos are observed. Which kind of objective does produce it?

  • a) Apochromatic
  • b) Achromatic
  • c) Semi-apochromatic
  • a) Fluorite

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