a. The light from a 220-W lamp spreads uniformly in all directions. Find the irradiance of...

a. The light from a 220-W lamp spreads uniformly in all directions. Find the irradiance of these optical electromagnetic waves and the amplitude of their -field at a distance of 10 m from the lamp. Assume that 5% of the lamp energy is converted to light.

---

b. Suppose a 2000-W laser beam is concentrated by a lens into a cross-sectional area of about 1 × 10−6 cm2. Find the corresponding irradiance and amplitudes of the - and -fields there.