ment, as in Figure 6-10, the bending is toward the nor¬mal to hie interface. Bending away from the normal oc¬curs when the beam passes from a more dense to a less dense medium.
The extent of refraction is given by Snell’s law:
6.12
If Ml in Figure 6-10 is a vacuum, Vi is equal to c, and T|j is unity (see Equation 6-11); with rearrangement, Equa¬tion 6-12 simplifies to
6.13
The refractive indexes of substance M2 can then be computed from measurements of (0i)vac and 02- For convenience, refractive indexes are usually measured and reported with air, rather than a vacuum, as the refer-ence. The refractive index is then
6.14
Most compilations of refractive indexes provide data in terms of Equation 6-14. Such data are readily converted to refractive indexes with vacuum as a refer¬ence by multiplying by the refractive index of air rela¬tive to a vacuum. That is,
6B-9 Reflection of Radiation
When radiation crosses an interface between media that differ in refractive index, reflection always occurs. The fraction of radiation reflected becomes greater with in¬creasing differences in refractive index. For a beam that enters an interface at right angles, the fraction reflected is given by
6.15
where Io is the intensity of the incident beam and Ir is the reflected intensity; T|1 and าๅ2 are the refractive in-dexes of the two media.
EXAMPLE 6-2
Calculate the percent loss of intensity due to reflec¬tion of a perpendicular beam of yellow light as it passes through a glass cell that contains water. As¬sume that for yellow radiation the refractive index of glass is 1.50, of water is 1.33, and of air is 1.00.
The total reflective loss will be the sum of the losses occurring at each of the interfaces. For the first interface (air to glass), we can write
ment, as in Figure 6-10, the bending is toward the nor¬mal to hie interface. Bending away from the normal oc¬curs when the beam passes from a more dense to a less dense medium.The extent of refraction is given by Snell’s law:6.12If Ml in Figure 6-10 is a vacuum, Vi is equal to c, and T|j is unity (see Equation 6-11); with rearrangement, Equa¬tion 6-12 simplifies to6.13The refractive indexes of substance M2 can then be computed from measurements of (0i)vac and 02- For convenience, refractive indexes are usually measured and reported with air, rather than a vacuum, as the refer-ence. The refractive index is then6.14Most compilations of refractive indexes provide data in terms of Equation 6-14. Such data are readily converted to refractive indexes with vacuum as a refer¬ence by multiplying by the refractive index of air rela¬tive to a vacuum. That is,6B-9 Reflection of RadiationWhen radiation crosses an interface between media that differ in refractive index, reflection always occurs. The fraction of radiation reflected becomes greater with in¬creasing differences in refractive index. For a beam that enters an interface at right angles, the fraction reflected is given by6.15where Io is the intensity of the incident beam and Ir is the reflected intensity; T|1 and าๅ2 are the refractive in-dexes of the two media.EXAMPLE 6-2คำนวณเปอร์เซ็นต์สูญเสียความเข้มเนื่องจาก reflec¬tion เป็นเส้นแสงสีเหลืองผ่านเซลล์แก้วที่ประกอบด้วยน้ำ As¬sume ที่สำหรับรังสีสีเหลืองดรรชนีหักเหของแก้ว 1.50 น้ำ เป็น 1.33 และอากาศเป็น 1.00ยอดขาดทุนสะท้อนแสงจะมีผลรวมของการสูญเสียที่เกิดขึ้นในแต่ละอินเทอร์เฟส แรกอินเทอร์เฟซ (อากาศกับแก้ว), เราสามารถเขียน
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