A ray passes from air (n=1) to water (n=1.33) and then intocrown glass (n=1.52).

Question

A ray passes from air (n=1) to water (n=1.33) and then intocrown glass (n=1.52). The light also reflects off the water and theglass. Wavelength of light = What is the minimum thickness of water that creates brightlight reflecting back out into the air? A ray passes from air (n=1) to water (n=1.33) and then intocrown glass (n=1.52). The light also reflects off the water and theglass. Wavelength of light = What is the minimum thickness of water that creates brightlight reflecting back out into the air?

Explanation / Answer

When a light ray incident the air water interface thenreflected ray r1 undergoes a phase changeof '' that is path differnece of /2  and another ray r2 from water glassinterface undergoes a phase change of '' that ispath differnece of /2 . Then for bright light to occur there should be contructive interfernce between the light rays. Then 2nt = m For minimum thickness m =1                                    n =1.33                  Then 2* 1.33 * t =                    Then t = /2.66

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