1 fast slow 550 nm Accessory plates Tell you fast vs. slow directionsTell you fast vs. slow directions –Fig. 7.21, p. 129 Can add or subtract retardation:Can add or subtract retardation: –Gypsum plate has Δ = 550 nm (“  ”) –Mica plate has Δ = 138 nm (“  /4”) Short dimension is always slowShort dimension is always slow 100 nm 450 nm

2 Accessory plates Tell you fast vs. slow directionsTell you fast vs. slow directions –Fig. 7.21, p. 129 Can add or subtract retardation:Can add or subtract retardation: –Gypsum plate has Δ = 550 nm (“  ”) –Mica plate has Δ = 138 nm (“  /4”) Short dimension is always slowShort dimension is always slow 100 nm 650 nm fast slow 550 nm

3 Using accessory plates 1) Find vibration directions, using extinction1) Find vibration directions, using extinction 2) Rotate so vibration directions are “diagonal”2) Rotate so vibration directions are “diagonal” 3) Insert plate3) Insert plate 4) If colors “add”, slow mineral || slow plate, otherwise, slow mineral || fast plate4) If colors “add”, slow mineral || slow plate, otherwise, slow mineral || fast plate XP Δ=200 nm

4 Using accessory plates 1) Find vibration directions, using extinction1) Find vibration directions, using extinction 2) Rotate so vibration directions are “diagonal”2) Rotate so vibration directions are “diagonal” 3) Insert plate3) Insert plate 4) If colors “add”, slow mineral || slow plate, otherwise, slow mineral || fast plate4) If colors “add”, slow mineral || slow plate, otherwise, slow mineral || fast plate p q XP

5 Using accessory plates 1) Find vibration directions, using extinction1) Find vibration directions, using extinction 2) Rotate so vibration directions are “diagonal”2) Rotate so vibration directions are “diagonal” 3) Insert plate3) Insert plate 4) If colors “add”, slow mineral || slow plate, otherwise, slow mineral || fast plate4) If colors “add”, slow mineral || slow plate, otherwise, slow mineral || fast plate p q XP 45°

6 Using accessory plates 1) Find vibration directions, using extinction1) Find vibration directions, using extinction 2) Rotate so vibration directions are “diagonal”2) Rotate so vibration directions are “diagonal” 3) Insert plate3) Insert plate 4) If colors “add”, slow mineral || slow plate, otherwise, slow mineral || fast plate4) If colors “add”, slow mineral || slow plate, otherwise, slow mineral || fast plate p q XP

7 Using accessory plates 1) Find vibration directions, using extinction1) Find vibration directions, using extinction 2) Rotate so vibration directions are “diagonal”2) Rotate so vibration directions are “diagonal” 3) Insert plate3) Insert plate 4) If colors “add”, slow mineral || slow plate, otherwise, slow mineral || fast plate4) If colors “add”, slow mineral || slow plate, otherwise, slow mineral || fast plate p q XP p = slow Δ=750 nm