Mrs. Rashmi Singh broke her reading glasses. When she went to the shopkeeper to order new specs, he suggested that she should get spectacles with plastic lenses instead of glass lenses. On getting the new spectacles, she found that the new ones were thicker than the earlier ones. She asked this question to the shopkeeper but he could not offer satisfactory explanation for this. At home, Mrs. Singh raised the same question to her daughter Anuja who explained why plastic lenses were thicker.
A. Write two qualities displayed each by Anuja and her mother.
B. How do you explain this fact using lens maker’s formula?
A. The qualities displayed by Anuja is that, she is a knowledgeable student who knows how to apply scientific concepts in daily life applications and is also a co-operative person, and the qualities of her mother is that she is a curious and alert person, she noticed that the thickness of the lenses are increased while the power of the lens was same and she wanted to know about the scientific reason for it.
B. We know that the lensmaker’s formula is,
Where, f is the focal length, 
is the refractive index of material lens w.r.t material of the surroundings, R1 is the radius of curvature of first surface and R2 is radius of curvature of second surface of the lens, here as the material of the lens is changed from glass to plastic, the refractive index also changes and to maintain the same focal length, the value of R1 and R2 must also change, that is why the lenses are a bit thicker than previous.
Couldn't generate an explanation.
Generated by AI. May contain inaccuracies — always verify with your textbook.
