Abstract: There are four parts in this paper. First, more discussions about the formulas and the physical situations are presented to the article “Condition of half-wave loss when light is emitted from optically denser medium to optically thinner medium”, which was published in this magazine not long ago. Second, some views about half-wave loss in that article are discussed. It is pointed out that there is usually no half-wave loss when the light with polarization parallel to the plane of incidence shooting on the medium with small refractive index from the medium with large refractive index and the ratio between their refractive indexes is huge. Third, the quantitative analysis of the interference of thin film is presented. It is shown that the results from the formulas in the textbook are usually close to the results from the Fresnel formula. Fourth, it is pointed out that the formula of the interference of thin film for the dark lines in the textbook is right, but to the bright lines, it will be absolutely wrong in some cases. 

Key words: Fresnel formula, half-wave loss, interference of thin film