\\\\(A = A_0 e^{-\\gamma t}\\\\)\\\\(A = \\dfrac{A_0}{2}\\\\) after 10 oscillations\\\\(\\because \\\\) After 2 seconds\\\\(\\dfrac{A_0}{2} = A_0 e^{-\\gamma (2)}\\\\)\\\\(2 = e^{2 \\gamma}\\\\)\\\\(\\ell n 2 = 2 \\gamma \\\\)\\\\(\\gamma = \\dfrac{\\ell n 2}{2}\\\\)\\\\(\\because A = A_0 e^{-\\gamma t}\\\\)\\\\(\\ell n \\dfrac{A_0}{A} = \\gamma t\\\\)\\\\(\\ell n 1000 = \\dfrac{\\ell n 2}{2} t\\\\)\\\\(2 \\left(\\dfrac{3 \\ell n 10}{\\ell n2} \\right) = t\\\\)\\\\(\\dfrac{6 \\ell n 10}{\\ell n 2} = 1\\\\)\\\\(t = 19.931 sec\\\\)\\\\(t \\approx 20 \\, sec\\\\)