Q. 295.0( 5 Votes )
You have two lenses A and B of focal lengths + 10 cm and – 10 cm respectively. State the nature and power of each lens. Which of the two lenses will form a virtual and magnified image of an object placed 8 cm from the lens? Draw a ray diagram to justify your answer.
Object distance u= 8 cm
Focal length of A = 10 cm
= 0.10 m
Focal length of B = -10 cm
= -0.10 m
Power of lens A = 10 Dioptres.
Since the power of lens A is positive so it is a convex lens.
Power of lens B= -10 Dioptres.
Since the power of lens b is negative so it is a concave lens.
We know that lens formula is:
Substituting the values of lens A in formula
Substituting the values of lens B in above lens formula:
Thus, lens A which is convex will form a virtual and magnified image of an object placed 8 cm from the lens i.e. between focus and pole of lens.
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