What is the total energy transported per hour along a narrow cylindrical laser beam 1.80 mm in diameter, whose B-field has an rms strength of

Am assuming the  B-field has an rms strength of 1.10×10−10T which was omitted

 E=1.686 x10⁻⁸J/hr

Explanation:

Intensity for electromagnetic wave is given as

I= cε₀(Emax)² equation 1

Also

B=Emax/c   equation 2

puting the value of B in equation 2 in equation 1 becomes

I= cε₀(Emax)²

I= c³ε₀B²

where

c = speed of light = 3 X 10⁸m/s

ε₀=permittivity of free space =8.85x 10-12 F m-1

B=1.10×10−10T

I= (3 X 10⁸m/s)³ X (8.85 X 10⁻12F/m) x(1.10×10−10T)²

I=2.891 X 10⁻⁶ W/m²

Energy per unit hour

E= IAt

= 2.891 X 10⁻⁶ W/m² x πr²x 3600

2.891 X 10⁻⁶ W/m² x 3.142 x ( 1.80 x 10⁻³/2) x(3600/1hr)

E=1.686 x10⁻⁸J/hr