Question

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?

Answer 1

Answer:

Explanation:

1. Compassionate

2. IDK

Answer 2

•A. qualitues displayed by

Anuja : Helping nature & Application of knowledge

Mother : Curiousity & awareness

•B. Len's maker formula

1/V - 1/U =( u-1)(1/R1 - 1/R2)

from here , we know

1/f = (u-1)(1/R1 - 1/R2)

•for glass

1/f = [u(glass) -1](1/R1 - 1/R2)

•for plastic

1/f = [u(plastic) -1](1/R1 - 1/R2)

•f is inversely proportional to refractive index of material of lens.

also u(glass) > u(plastic)

•so, focal length of plastic lens is increased

but for same focal length of thickness of lens should also be increased .