Question

Cora lies in a tanning bed getting a tan. Suppose that AS = 0.79 m2 of her skin is exposed to the light from the ultraviolet (UV) lamps. The UV lamps produce light with an average energy density of uT = 5 x 10-6 J / m3. She lies in the bed for tT = 30 minutes. 

Randomized Variables
AS = 0.79 m2
UT = 5 x 10-6 J / m3
tT = 30 minutes

Part (a) compute the average intensity ST in W / m2 of the UV light.

Part (b) supposes that Cora’s skin absorbs 100% of the energy of the UV light. Calculate how much energy UT in J her skin absorbs during time she lies in the bed.

Part (c) computes the rms electric field ET in N/C of UV light.

Part (d) computes the rms magnetic field BT in T of the UV light.

An antenna with power P = 1.4 x 103 W is radiating spherical electromagnetic waves. Consider a place which is d = 190 m away from the antenna. 

Randomized Variables
P = 1.4 x 103 W
d = 190 m

1. Express I in terms of the electric field magnitude Emax, and the speed of light c.

2. Find Emax2 in terms of P, d, and c.

3. Solve for numerical value of Emax in V/m.