Question

2. Human night vision is very sensitive to blue light but is relatively unaffected by red light. (For this reason, many flashlights intended for use while camping or hiking have a red light setting which won't affect your ability to see in the darkness of night.) You wish to design a reflective sign which will be visible at night, but not harm the viewer's night vision. The sign will have a white reflective backing and will be coated by polycarbonate with index of refraction 1.60. a) For what minimum thickness of polycarbonate will the viewer see no 445 nm light (blue) reflected from the sign? b) For what minimum thickness of polycarbonate will the viewer see no 445 nm light and the maximum amount of 685 nm (red) light? -

Answer 1

Solo 1.60 given schrective Indest= do(blue) 445 92 blue light If no q blue light gets retrached, it means should undergo distriuctive Interference Condition For desterective Interterence is tact md (m=0,1,2,..) a hreff tmin (mall = 18445 139.06 hm 2.x1-60 Condition for constrrective interference is (b) the teons (mtlad (m, 0,1,2,...) 2 hello tcons 13a1nm (6+12) x 685 2 X 1.60 Now tdist lox445 1390.6hna 13910m rmalo) 2x160 the required thicknessas Ibainm