# Electric field strength from a light bulb

1. Feb 22, 2008

### A90

1. The problem statement, all variables and given/known data
What is the approximate electric field strength of the electromagnetic waves radiated by a 100-W light bulb, measured 3.0m from the bulb?

2. Relevant equations
$$\vec{E}$$=$$\frac{kq}{d^{2}}$$

P=$$\frac{2kq^{2}a^{2}}{3c^{3}}$$

3. The attempt at a solution
I solved for q=$$\sqrt{\frac{3Pc^{3}}{2ka^{2}}}$$, and then plugged that into the equation for electric field, and I have all the values I need to solve except for the acceleration, which I'm not sure how to find. I thought about using the second derivative of x(t)=xsin$$\omega$$t, but I don't know what to use for x, $$\omega$$ or t.