Answer
Given,
refractive index of film, n = 1.6
refractive index of air, n' = 1
angle of incidence, i = 35°
angle of refraction, r = ?
Using Snell's law
n' sin i = n sin r
1 x sin 35° = 1.6 x sin r
r = 21°
Angle of refraction is equal to 21°.
Now,
distance at which refractive angle comes out
d = 2.5 mm
α be the angle with horizontal surface and incident ray.
α = 90°-21° = 69°
t be the thickness of the film.
So,
t = 2.26 mm
Hence, the thickness of the film is equal to 2.26 mm.
Answer:
Total heat transfer rate is combined convection and radiation transfer rate, multiplied with absorptivity factor. From that equation you can find temperature of the roof using iteration method.
Explanation:
<u>Known:</u>
steel sheet roof emissivity ∈ = 0.13
steel sheet roof absorptivity _s = 0.65
air temperature T∞ = 16°C ...= 289K
heat transfer rate = 750 W/m2
natural convection h = 7W/m2K
Total heat transfer rate is combined heat transfer rate of convection and radiation, multiplied with absorptivity factor:
=
T∞-
)+∈σA(
-
T∞)-∈σ(
=0
2562-7-7.371*10^-9=0
Use iteration method to solve for
=350.17 K...=77.17°C
In this particular situation, cat would not be comfortable with walking on a roof since its surface temperature is 77.17°C which may even cause burns to its paws.