A typical laser used in introductory physics laboratories produces a continuous beam of light about 1.0 mm in diameter. The average power of such a laser is 0.75 mW.
(i) What is the average intensity?
(ii) What is the peak intensity?
(iii) What is the average energy density of this beam?
(iv) If the beam is reflected from a mirror, what is the maximum force the laser beam can exert on it?
(v) Describe the orientation of the laser beam relative to the mirror for the case of maximum force.
4 answers
Damon?? can you help me out on this one please
I have this same question, hope you get the answer
well, it is late but I might be able to point a direction
average intensity
= average power / (pi r^2)
Peak = twice average power if a sine wave
[ average of sin^2 = (1/2) ]
energy density usually in Joules per square centimeter where it hits I assume per second. That would be the power * c /pi r^2
The maximum force is when the light is reflected straight back, changing in momentum from plus to minus
The maximum force is twice the momentum of the beam times c which is how much hits per second.
average intensity
= average power / (pi r^2)
Peak = twice average power if a sine wave
[ average of sin^2 = (1/2) ]
energy density usually in Joules per square centimeter where it hits I assume per second. That would be the power * c /pi r^2
The maximum force is when the light is reflected straight back, changing in momentum from plus to minus
The maximum force is twice the momentum of the beam times c which is how much hits per second.
The relation between the energy and the momentum is
E = p c where p is momentum
so our momentum density here is our energy density/c
E = p c where p is momentum
so our momentum density here is our energy density/c
1 answer