What's is the difference between predicted speed and actual speed

Adouble-slit experiment is performed with light of wavelength 600 nm. the bright interference fringes are spaced 1.8 mm apart on the viewing screen. what will the fringe spacing be if the light is changed to a wavelength of 400 nm? ?

Ammonia enters the expansion valve of a refrigeration system at a pressure of 10 bar and a temperature of 18oc and exits at 6.0 bar. the refrigerant undergoes a throttling process. determine the temperature, in oc, and the quality of the refrigerant at the exit of the expansion valve.

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