The milkman shifts the pH of the fresh milk from 6 to slightly alkaline (to decrease the rate of fermentation) because in alkaline condition milk does not set as curd easily.

Magnification obtained by a lens is the ratio of height of image (h₁) to the height of object (h₂) i.e., Magnification, m= h₁/h₂

When we cut sphere, two parts we got and here spherical mirror is formed. But remember, applying silvering colour or agent either the inside or outside surface.

(i) Pb + CuCl₂ → PbCI₂ + Cu (ii) Na₂SO₄ + BaCl₂ → BaSO₄ + 2NACI (iii) C+ O₂ → CO₂ (iv) CH₄ + 20₂ → CO₂ + 2H₂ O