PPT Slide
What is phase difference between rays 1 and 2 ?
ray 2 travels further => phase difference due to path difference
phase difference due to extra thickness is (2?/?`)(2t)
but ?` is the wavelength in the water medium! ?` = ?/n
ray 1 is reflected from a medium with slower speed
ray 2 is reflected from a medium with higher speed
extra phase difference of ? due to reflection of ray 1
total phase difference ? = ? + (2?n/?)(2t)