Q24.A convergent doublet of separated lenses, corrected for spherical aberration, has resultant focal length of 10 cm. The separation between the two lenses is 2 cm . The focal lengths of the component lenses (1) 18 cm, 20 cm (2) 10 cm, 12 cm (3) 12 cm, 14 cm (4) 16 cm, 18 cm
What This Question Tests
This problem requires applying the formula for the equivalent focal length of two separated lenses and using the condition for correction of spherical aberration to find the individual focal lengths.
Concepts Tested
Formulas Used
1/F = 1/f₁ + 1/f₂ - d/(f₁f₂)
d = f₁ - f₂ (for spherical aberration correction)
📚 NCERT Sections This Tests
9.7 — Double-Convex Lenses Are To Be Manufactured From A Glass Of
Physics Class 12 · Chapter 9
9.7 Double-convex lenses are to be manufactured from a glass of refractive index 1.55, with both faces of the same radius of curvature. What is the radius of curvature required if the focal length is to be 20cm?
9.20 — (A) Determine The ‘Effective Focal Length’ Of The Combination Of
Physics Class 12 · Chapter 9
9.20 (a) Determine the ‘effective focal length’ of the combination of the two lenses in Exercise 9.10, if they are placed 8.0cm apart with their principal axes coincident. Does the answer depend on which side of the combination a beam of parallel light is incident? Is the notion of effective focal length of this system useful at all? (b) An object 1.5 cm in size is placed on the side of the convex lens in the arrangement (a) above. The distance between the object and the convex lens is 40 cm. Determine the magnification produced by the two-lens system, and the size of the image.
9.8 — A Beam Of Light Converges At A Point P. Now A Lens Is Placed In The
Physics Class 12 · Chapter 9
9.8 A beam of light converges at a point P. Now a lens is placed in the path of the convergent beam 12cm from P. At what point does the beam converge if the lens is (a) a convex lens of focal length 20cm, and (b) a concave lens of focal length 16cm?
📋 Question Details
- Chapter
- Ray Optics
- Topic
- Combination of lenses
- Year
- 2018
- Shift
- 15 Apr Shift 2 Online
- Q Number
- Q24
- Type
- MCQ
- NCERT Ref
- Class 12 Physics Ch 9: Ray Optics and Optical Instruments
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