Ha The Expert TA l Human-i x C Secure /common/TakeTu alAssignment aspx (14%) Pro

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Ha The Expert TA l Human-i x C Secure /common/TakeTu alAssignment aspx (14%) Problem 4: Cora lies in a tanning bed getting a tan. Assume that As 0.52 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 4.8 x 1016 J m3. She lies in the bed for 25 minutes. Randomized Variables As 0.52 m Assignment Status 4.8 x 25 minutes Click here for 4 25% Part (a) Calculate the average intensity ST in W m3 of the UV light. detailed vie Grade Summary Deductions Potential 100% Problem Status sino coso tano 8 9 Submissions Completed Attempts remaining: 2 Completed cotano asino acoso per attempt) 1 2 3 detailed view Partia atano acotano sinh END Degrees Radians BACK SPACT CLEAR Submit Feedback: S% deduction per feedback. Hints i A 25 Part (b) If Cora's skin absorbs 100% of the energy of the UV light, calculate how much energy Vin J her skin would absorb during the time she lies in the bed. i 25% Part (c) Calculate the rms electric field. ETin NAC of the UV light. A 25% Part (d) Calculate the rms magnetic field B in T of the UV light. TA LLC 3:31 PM

Explanation / Answer

(a)

Average intensity of the UV light is,

ST = uT * c

ST = 4.8*10^(-6)*3*10^8 = 1440 W/m^2

(b)

Total energy absorbed by the skin is,

U = ST*AS*tT

U = 1440*0.52*25*60

U = 11.23*10^5 J

(c)

We know that,

uT = e0*ET^2

where, uT = average energy density

ET =  rms electric field

ET = sqrt (4.8*10^(-6) / 8.85*10^(-12))

ET = 736.46 N/C

(d)

rms magnetic field is,

BT = ET / c

BT = 736.46 / 3*10^8

BT = 2.45*10^(-6) T

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