Answer:
a) I = 1,894 10¹⁰ W / m², b) E = 1.376 10⁵ N / C
Explanation:
a) intensity is defined as energy per unit area per unit time
I = P / A
let's reduce the magnitudes to the SI system
P = 10 mW = 10 10⁻³ W
d = 0.82 μm = 0.82 10⁻⁶ m
the laser area is
A =π r² = π d²/4
A =π (0.82 10⁻⁶)²/4
A = 5.28 10⁻¹³ m²
we calculate
I =
I = 1,894 10¹⁰ W / m²
b) average intensity and electric field are related
I = E * E
E = √I
E =
E = 1.376 10⁵ N / C
Answer:
0.88 cm
Explanation:
Initial length at 10°c, L = 23 m
Rise of temperature, Δt = 42 - 10 = 32°c
Coefficient of linear expansion of concrete, α = 12 x 10^(-6) per°c
Minimum spacing to be left = α L Δt
= 8.832 x 10^{-1} cm
= 0.88 cm
Note: I have a chosen a general value of 12 x 10^-6 per deg c for coefficient of expansion of concrete. However, please refer to the value given in your text book and substitute it for an accurate answer.
Answer:
It's 1.0000042 times longer in summer than in winter. It represents a 1.6 centimeters difference between seasons.
Explanation:
The linear coefficient of thermal expansion for steel is about . From the equation of linear thermal expansion, we have:
Taking the winter day as the initial, and the summer day as the final, we can take the relationship between them:
It means that the bridge is 1.0000042 times longer in summer than in winter. If we multiply it by the length of the bridge, we obtain that the difference is of about 1.6 centimeters between the two seasons.