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- Homework Statement
- The amplitude of the oscillating electric field at your cell phone is 4.0 μV/m when you are 10 km east of the broadcast antenna. What is the electric field amplitude when you are 20 km east of the antenna

- Homework Equations
- electric field

**Homework Statement:**The amplitude of the oscillating electric field at your cell phone is 4.0 μV/m when you are 10 km east of the broadcast antenna. What is the electric field amplitude when you are 20 km east of the antenna

**Homework Equations:**electric field

i've done

E=##\frac A {r^\left(2\right)}##

that in this case is ##4 \times 10^\left(-6 \right)=\frac A {10000^2} ##

i solve for A

##A= 4 \times 10^\left(-6\right) \times 10000^2##

then i divide ##A## by ##20000^2##

but i do not get the right result, why?