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ฟิสิกส์โอลิมปิก วิทยาศาสตร์โอลิมปิก ข้อสอบแข่งขัน ข้อสอบชิงทุน => GRE - Physics => Topic started by: conantee on January 06, 2010, 01:34:44 PM



Title: GR8677.073
Post by: conantee on January 06, 2010, 01:34:44 PM
73. It is necessary to coat a glass lens with a non-reflecting layer. If the wavelength of the light in the coating is \lambda, the best choice is a layer of material having an index of refraction between those of glass and air and a thickness of
(A) \frac{\lambda}{4}
(B) \frac{\lambda}{2}
(C) \frac{\lambda}{\sqrt{2}}
(D) \lambda
(E) 1.5 \lambda