Mrs. Rashmi Singh broke her reading glasses. When she went to the shopkeeper to order new spectacles, 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 a satisfactory explanation. 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 the lens maker's formula?
(a) Write two qualities displayed each by Anuja and her mother.
(b) How do you explain this fact using the lens maker's formula?
Solution
(a) \emph{Anuja}: scientific temperament, knowledgeable, cooperative/helpful. \emph{Mother}: inquisitive, keen to learn, has a questioning (scientific) attitude.
(b) By the lens maker's formula , the power required for Mrs. Singh is fixed. Plastic has a \emph{smaller} than glass, so is smaller; to keep the same, must be larger, i.e. the radii of curvature must be \emph{smaller} (more curved surfaces).
(b) By the lens maker's formula , the power required for Mrs. Singh is fixed. Plastic has a \emph{smaller} than glass, so is smaller; to keep the same, must be larger, i.e. the radii of curvature must be \emph{smaller} (more curved surfaces).
CBSE Class 12 Board · 2017 · Delhi · Subjective