A laser has a power of 21.0 W and a beam radius of 0.458 mm. (a) Find the intens

Question

A laser has a power of 21.0 W and a beam radius of 0.458 mm.

(a) Find the intensity of the laser. W/m2

(b) Suppose you were floating in space and pointed the laser beam away from you. What would your acceleration be? Assume your total mass, including equipment, is 72.2 kg and that the force is directed through your center of mass. Hint: The change in momentum is the same as in the nonreflective case. m/s2

(c) Calculate your acceleration if it were due to the gravity of a space station with mass 1.07 106 kg and center of mass 102.5 m away. m/s2

(d) Calculate the peak electric and magnetic fields of the laser.

Emax =

Bmax =

Explanation / Answer

P = 21 W

r = 0.458 mm

A = pi*r^2 = 6.6*10^-7 m^2

(a) I = P/A = 21/6.6*10^-7 = 3.2*10^7 W/m^2

(b) m = 72.2 kg

      F = 2IA/c ======> a = F/m = (2IA)/(mc) = 1.95*10^-9 m/s^2

(c) M = 1.07*10^6 kg

     R = 102.5 m

     Acceleration = a = GM/R^2 = (6.67*10^-11*1.07*10^6)/(102.5)^2

                             a = 6.8*10^-9 m/s^2

(d) Emax = sqrt(2*uo*c*I) = sqrt(2*4pi*10^-7*3*10^8*3.2*10^7)

                = 1.55*10^5 N/C

    Bmax = Emax/c = 1.55*10^5/3*10^8 = 5.2*10^-4 T

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