Image in Thick LensHardQuestion 20251
Question
For a thick lens or lens system, the principal planes (H and H') are the reference planes from which:
- AAll distances are measured to the lens centre
- BObject distance (from H) and image distance (from H') are measured and obey the thin lens formulaCorrect
- CFocal lengths are measured
- DThe lens maker's formula is applied
Correct answer
Object distance (from H) and image distance (from H') are measured and obey the thin lens formula
Explanation
For a thick lens or system of lenses, the equivalent thin lens formula 1/v − 1/u = 1/f holds only when u is measured from the front principal plane H and v is measured from the rear principal plane H'. The principal planes are where the equivalent thin lens is 'located'.