(a) [tex]3.3\cdot 10^{-6} Pa[/tex]
The radiation pressure exerted by an electromagnetic wave on a surface that totally absorbs the radiation is given by
[tex]p=\frac{I}{c}[/tex]
where
I is the intensity of the wave
c is the speed of light
In this problem,
[tex]I=1000 W/m^2[/tex]
and substituting [tex]c=3\cdot 10^8 m/s[/tex], we find the radiation pressure
[tex]p=\frac{1000 W/m^2}{3\cdot 10^8 m/s}=3.3\cdot 10^{-6}Pa[/tex]
(b) [tex]4.4\cdot 10^{-8} m/s^2[/tex]
Since we know the cross-sectional area of the laser beam:
[tex]A=6.65\cdot 10^{-29}m^2[/tex]
starting from the radiation pressure found at point (a), we can calculate the force exerted on a tritium atom:
[tex]F=pa=(3.3\cdot 10^{-6}Pa)(6.65\cdot 10^{-29} m^2)=2.2\cdot 10^{-34}N[/tex]
And then, since we know the mass of the atom
[tex]m=5.01\cdot 10^{-27}kg[/tex]
we can find the acceleration, by using Newton's second law:
[tex]a=\frac{F}{m}=\frac{2.2\cdot 10^{-34} N}{5.01\cdot 10^{-27} kg}=4.4\cdot 10^{-8} m/s^2[/tex]
