Question

A thin layer of oil (n = 1.40) floats on the surface of a puddle of water (n = 1.33). One part of the oil film appears bright greenish-blue, i.e. it strongly reflects light with a wavelength in vacuum of 497 nm. What is the smallest nonzero film thickness of the oil film in this region?

Group of answer choices

207 nm

89.0 nm

124 nm

249 nm

178 nm

Answer 1

strongly reflects means constructive interference.

Minimum thickness is given as

t = ( m + 1/2) $\lambda$ / 2n

put m = 0

t = ( 0 + 1/2) 497 / 2 * 1.40

t = 88.75 nm

Answer 2

Solution phase No phase diange. n=1 drenge. lelhen clignt comes from raver medium and get refleeted from densen meclium then phase change of No=1.40) OCC wyl No - 1.33 Hore net phase change = a so condition for Constructive interyerenee. 20p it = 1m+t (m+3) 1 for smallest thickness m=0 ta ANF given J= 4979m ng=1.40 = 88.75mm 497 nm - t- 4X4.40 to 89.0nm Answer

Answer 3

Solution phase No phase diange. n=1 drenge. lelhen clignt comes from raver medium and get refleeted from densen meclium then phase change of No=1.40) OCC wyl No - 1.33 Hore net phase change = a so condition for Constructive interyerenee. 20p it = 1m+t (m+3) 1 for smallest thickness m=0 ta ANF given J= 4979m ng=1.40 = 88.75mm 497 nm - t- 4X4.40 to 89.0nm Answer