jasminebrown72
05.08.2020 •
Physics
Lasers are classified according to the eye-damage danger they pose. Class 2 lasers, including many laser pointers, produce visible light with no greater than 1.0 mW total power. They're relatively safe because the eye's blink reflex limits exposure time to 250 ms.
Requried:
a. Find the intensity of a 1-mW class 2 laser with beam diameter 2.0 mm .
b. Find the total energy delivered before the blink reflex shuts the eye.
c. Find the peak electric field in the laser beam.
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Ответ:
(a) The intensity of laser beam is .
(b) The total energy delivered before the blink reflex shuts the eye is .
(c) The required value of peak electric field in the laser beam is .
Given data:
The power of laser is, .
The exposure time is, .
The beam diameter is, .
a)
The standard expression for the intensity of beam is given as,
I = P/A
Here, P is the power of the laser and A is the cross-sectional area of the beam. And its value is,
Then intensity is,
Thus, the intensity of laser beam is .
(b)
The expression for the total energy delivered is given as,
E = Pt
Solving as,
Thus, the total energy delivered before the blink reflex shuts the eye is .
(c)
The expression for the peak electric field is given as,
Solving as,
Thus, the required value of peak electric field in the laser beam is .
Learn more about the laser intensity here:
link
Ответ:
a) 318.2 W/m^2
b) 2.5 x 10^-4 J
c) 1.55 x 10^-8 v/m
Explanation:
Power of laser P = 1 mW = 1 x 10^-3 W
exposure time t = 250 ms = 250 x 10^-3 s
If beam diameter = 2 mm = 2 x 10^-3 m
then
cross-sectional area of beam A = = (3.142 x )/4
A = 3.142 x 10^-6 m^2
a) Intensity I = P/A
where P is the power of the laser
A is the cros-sectional area of the beam
I = ( 1 x 10^-3)/(3.142 x 10^-6) = 318.2 W/m^2
b) Total energy delivered E = Pt
where P is the power of the beam
t is the exposure time
E = 1 x 10^-3 x 250 x 10^-3 = 2.5 x 10^-4 J
c) The peak electric field is given as
E =
where I is the intensity of the beam
E is the electric field
c is the speed of light = 3 x 10^8 m/s
= 8.85 x 10^9 m kg s^-2 A^-2
E = = 1.55 x 10^-8 v/m
Ответ: