What is meant by power of a lens ? Define its S.I. unit.
Light (10)What is meant by power of a lens ? Define its S.I. unit.
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.
Answer
Power of lens: Ability of a lens to converge or diverge the light rays falling on it/ The degree of convergence or divergence of light rays achieved by a lens/ Reciprocal of focal length of the lens.
1 dioptre - It is the power of a lens whose focal length is 1 metre.
In this case the object will be between the optical centre and principal focus of the lens. Hence the convex lens, i.e., lens A will form virtual and magnified image of the object.
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