Answer:
Explanation:
Point beneath you forms a beautiful iridescent green
refractive index of Gasoline 
Wavelength of Green light is 
Here light first traverse from air(n=1) to gasoline , it reflects from front surface of gasoline(n=1.38) so it suffers a phase change. After this light reflect from rear surface of gasoline and there is a decrease in refractive index(n=1.38 to n=1.33), so there is no phase change occurs .
For constructive interference

here t= thickness of gasoline film
n=refractive index
for 


C., used in power plants I think.
Answer:
The paper does not catch fire when wrapped around aluminium pipe because aluminium absorbs the heat, so paper does not attain its ignition temperature.
Explanation: