A beam of initially unpolarized light passes through a sequence of three ideal polarizers. The angle ϕ 12 between the axes of the first and second polarizers is 23.9 ∘ , and the angle ϕ 23 between the axes of the second and third polarizers is 51.3 ∘ . Three polarizing filters equally spaced along a line colinear with their central axes. The polarization axis of the first filter points straight up. The polarization axis of the second filter is rotated clockwise by an angle phi subscript 1 2 relative to the axis of the first filter. The polarization axis of the third filter is rotated clockwise by an angle phi subscript 2 3 relative to the axis of the second filter. The beam incident on the first filter has intensity I subscript 0. The beam transmitted by the third filter has intensity I subscript 3. What is the ratio of the intensity I 3 of light emerging from the third polarizer to the intensity I 0 of light incident on the first polarizer?

Can someone explain to me how to do this problem ?

An internally reversible refrigerator has a modified coefficient of performance accounting for realistic heat transfer processes of where qin is the refrigerator cooling rate, qout is the heat rejection rate, and is the power input. show that copm can be expressed in terms of the reservoir temperatures tc and th, the cold and hot thermal resistances rt,c and rt,h, and qin, as where rtot rt,c rt,h. also, show that the power input may be expressed as 1.39 a household refrigerator operates with cold- and hot-temperature reservoirs of tc 5 c and th 25 c, respectively. when new, the cold and hot side resistances are rc,n 0.05 k/w and rh,n 0.04 k/w, respectively. over time, dust accumulates on the refrigerator’s condenser coil, which is located behind the refrigerator, increasing the hot side resistance to rh,d 0.1 k/w. it is desired to have a refrigerator cooling rate of qin 750 w. using the results of problem 1.38, determine the modified coefficient of performance and the required power input w under (a) clean and (b) dusty coil conditions. internally reversible refrigerator qout qin w high-temperature reservoir low-temperature reservoir th th,i tc,i tc high-temperature side resistance low-temperature side resistance w qin th tc qinrtot tc qinrtot copm tc qinrtot th tc

In a good thermo flask the main cause of heat loss is