Answer:
a) I = 5.79 10⁵ W/m²
, b) I = 2.58 10² W / m², c) I = 8.03 10³ W / m²
, d) I = 5.3 10⁶ W / m², e) I = 9 10¹ W / m²
, f) D> A> C> B> E
Explanation:
The intensity is defined as the power per unit area
I = P / A
The area of a circle is
A = π r²
Laser A
Power P = 2.2 W
Diameter d = 2.9 mm = 2.9 10⁻³ m
Let's calculate
Area
A = π d² / 4
A = π (2.2 10⁻³)²/4
A = 3.80 10⁻⁶ m²
Let's calculate the intensity
I = 2.2 / 3.80 10⁻⁶
I = 0.579 10⁶ W / m²
I = 5.79 10⁵ W/m²
Laser B
The electric field is E = 440 V / m
Intensity average is
I = E B / 2 μ₀
The relationship of the fields with the speed of light
E / B = c
The intensity
I = EE / 2 μ₀ c
I = 440² / (2 4π 10⁻⁷ 3 10⁸)
I = 1.936 105/750
I = 2.58 10² W / m²
Laser C
The magnetic field amplitude B = 8.2 10⁻⁶ T
I = c / 2μ₀ B²
I = 3 10⁸/2 4π 10⁻⁷ (8.2 10⁻⁶)²
I = 8.03 10³ W / m²
Part D
Diameter d = 1.8 mm = 1.8 10⁻³ m
The radius is r = d / 2 = 0.9 10⁻³ m
The force is F = 9.0 10⁻⁸ N
The radiation pressure is on a reflective surface is
P = 2S / c
I = S =P c / 2
The definition of pressure is
P = F / A
I = F c / 2 A
I = 9.0 10⁻⁸ 3 10⁸ / (2π (0.9 10⁻³)²)
I = 5.3 10⁶ W / m²
Part E
Average energy density
u = 3.0 10⁻⁷ J / m³
I = S = c u
I = 3 10⁸ 3.0 10⁻⁷
I = 9 10¹ W / m²
Part F
Sort in descending order
The order is
D> A> C> B> E
