A swimmer enters a gloomier world (in one sense) on diving to greater depths. Given that the mean molar absorption coefficient of sea water in the visible region is 6.2 x 10-5- L moI-1 cm-1, calculate the depth at which a diver will experience (a) half the surface intensity of light, (b) one-tenth the surface intensity

Respuesta :

Answer: (a) The depth at which a diver will experience half the surface intensity of light is 0.81 m.

(b) The depth at which a diver will experience one-tenth the surface intensity is 2.69 m.

Explanation:

(a)  We know that Lambert-Beer's law is as follows.

    [tex]log_{10} = \frac{I_{o}}{I_{t}} = \epsilon \times c \times l[/tex]

As it is given that,

           [tex]\frac{I_{o}}{I_{t}} = 2[/tex]                

and,   [tex]\epsilon = 6.2 \times 10^{-3}[/tex]

We know that molarity of sea water is 599 mM.

   [tex]log_{10}(2) = 6.2 \times 10^{-5} \times 599 \times 10^{-3} \times l[/tex]

       l = [tex]\frac{0.301}{6.2 \times 10^{-5} \times 599 \times 10^{-3}}[/tex]

        = 81 cm

        = 0.81 m

Therefore, the depth at which a diver will experience half the surface intensity of light is 0.81 m.

(b)  We are given that,

              [tex]\frac{I}{I_{o}} = 10[/tex]

    [tex]log_{10}(10) = 6.2 \times 10^{-5} \times 599 \times 10^{-3} \times l[/tex]

                l = [tex]\frac{1}{6.2 \times 10^{-5} \times 599 \times 10^{-3} \times l}[/tex]

                  = 269 cm

or,               = 2.69 m       (as 1 m = 100 cm)

Therefore, the depth at which a diver will experience one-tenth the surface intensity is 2.69 m.