Pls solve this ques of physics...pls pls pls?

Two sinusoidal waves of equal amplitude are ¼ of a wavelength out of phase. What is the amplitude of the resultant wave? In young’s experiment, light of wavelength 6000Å is used to produce fringes of width 0.8mm at a distance of 2.5m. What will be the fringe width if the whole apparatus is dipped in a liquid of... show more Two sinusoidal waves of equal amplitude are ¼ of a wavelength out of phase. What is
the amplitude of the resultant wave? In young’s experiment, light of wavelength 6000Å
is used to produce fringes of width 0.8mm at a distance of 2.5m. What will be the fringe
width if the whole apparatus is dipped in a liquid of refractive index of 1.6?

An elastic material of Young’s modulus Y is subjected to a stress S. what will be the
elastic energy stored per unit volume of the material. Steel and copper wires of same
length are stretched by the same weight one after the other. Young’s modulus of steel
and copper are 2 x 1011 N/m2 and1.2 x 1011N/m2. What will be the ratio of increase in
length?


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