Question 867341
If you block 30% of the light, then the light intensity after it passes through the glass will be 100 - 30 = 70%. Therefore, L1(t) = 0.7*L0 (basically 70% of the original light intensity L0 coming in). Plug this is in and solve for t



{{{L1(t)= L0(10)^(-.034t)}}}



{{{0.7*L0= L0(10)^(-.034t)}}}



{{{0.7*L0/L0 = (L0(10)^(-.034t))/L0}}}



{{{0.7 = (10)^(-.034t)}}}



{{{ln(0.7) = ln((10)^(-.034t))}}}



{{{ln(0.7) = -0.034t*ln(10)}}}



{{{ln(0.7) = -0.034*ln(10)*t}}}



{{{ln(0.7)/(-0.034*ln(10)) = t}}}



{{{4.55593999958068 = t}}}



{{{t = 4.55593999958068}}} This is the approximate thickness.