The light intensity I​ (in lumens) at a depth of x feet in Lake Elizabeth is given by the formula log (StartFraction Upper I Over 12 EndFraction )equals negative 0.025 x . a. Find the light intensity at a depth of 24 feet. b. At what depth is the light intensity 7 ​lumens?

Respuesta :

Answer:

The light intensity at a depth of 24 feet is 3.0143 lumens.

The light intensity will be 7 lumenus at the depth of 9.3732 feet approximately.

Step-by-step explanation:

Consider the provided formula.

[tex]log(\frac{I}{12})=-0.025x[/tex]

Where I is the intensity of light and x is the depth.

Part (A) Find the light intensity at a depth of 24 feet.

Substitute x=24 in above formula.

[tex]log(\frac{I}{12})=-0.025(24)[/tex]

[tex]log(\frac{I}{12})=-0.6[/tex]

[tex]\frac{I}{12}=10^{-0.6}[/tex]

[tex]\frac{I}{12}=0.2512[/tex]

[tex]I=3.0143[/tex]

Hence, the light intensity at a depth of 24 feet is 3.0143 lumens.

Part (B) At what depth is the light intensity 7 ​lumens

Substitute I=7 in above formula.

[tex]log(\frac{7}{12})=-0.025x[/tex]

[tex]-0.23433=-0.025x[/tex]

[tex]0.23433=0.025x[/tex]

[tex]x=\frac{0.23433}{0.025}[/tex]

[tex]x=9.3732[/tex]

Hence, the light intensity will be 7 lumenus at the depth of 9.3732 feet approximately.