87) What speed should a galaxy move with respect to us so that the sodium line at 589.0 nm is observed at 589.6 nm?

88) Two slits are made one millimetre apart and the screen is placed one metre away. What is the fringe separation when bluegreen light of wavelength 500 nm is used?

89) A viewing screen is separated from a double-slit source by 1.2 m. The distance between the two slits is 0.030 mm. The second-order bright fringe m =2 is 4.5 cm from the center line. Wavelength of the light is

90) A viewing screen is separated from a double-slit source by 1.2 m. The distance between the two slits is 0.030 mm. The second-order bright fringe m =2 is 4.5 cm from the center line. Distance between adjacent bright fringes is

91) A light source emits visible light of two wavelengths:???= 430 nm and??' = 510 nm. The source is used in a double-slit interference experiment in which L = 1.5 m and d = 0.025 mm. separation distance between the third order bright fringes. is