1. Physics Lecture Resources
Prof. Mineesh Gulati
Head-Physics Wing
Happy Model Hr. Sec. School, Udhampur, J&K
Website: happyphysics.com
happyphysics.com

2. Ch 33 The Nature and Propagation of Light
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3. 33.1 The Nature of Light Speed of light=2.9792458x108m/s
Wave front: describe wave propagation
Rays
Rays
Source
Wave fronts
Wave fronts
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4. Physical optics: the branch dealing specifically with wave behavior
Geometric optics: the branch of optics which is used for the ray description.
Physical optics: the branch dealing specifically with wave behavior
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5. 33.2 Reflection and Refraction
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6. Reflection and Refraction
Incident rays
Normal θa θb θr
Refracted rays
Reflected rays
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7. Type of reflection
index of refraction
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8. law of reflection law of refraction
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9. wavelength of light in a material
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10. Example 33.2
The wavelength of the red light form a helium-neon laser is 633nm in air but 474nm in aqueous humor inside your eyeball. Calculate the index of refraction of the aqueous humor and the speed and frequency of the light in this substance.
ANS:
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11. 33.3 Total Internal Reflectionθb
Θb=90° nb na
>θcrit
θcrit θa P
critical angle for total internal reflection
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12. Application of total internal reflection
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13. 33.4 Dispersion
The dependence of wave speed and index of refraction on wavelength is called dispersion
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14. Dispersion of light by a prism
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15. Rainbow
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16. 33.5 Polarization
Polarization is a characteristic of all transverse waves.
Polarized in y-direction
Polarized in z-direction
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17. Polarizing filter
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18. A Polaroid filter is illuminated by unpolarized natural light
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19. Malus’s law, polarized light passing through an analyzer
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20. Polarization by reflection
Reflected light is 100% polarized perpendicular to the plane of incidence
Polarization by reflection
Natural light
Normal
Plane of incidence
Reflecting surface
Transmitted light is partially polarized parallel to the place of incidence

21. Brewster’s law for the polarizing angle
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22. 33.6 Scatttering of Light
When we look at the daytime sky, the light that we see is sunlight that has been absorbed and then re-radiated in a variety of directions. The process is called scattering.
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23. AA’ construct a new wave front BB’
33.7 huygens’ Principle
Every point of a wave front may be considered the source of secondary wavelets that spread out in all directions with a speed equal to the speed of propagation of the wave.
AA’ construct a new wave front BB’
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24. Light is an electromagnetic wave
Light is an electromagnetic wave. When emitted or absorbed, it also shows particle properties. It is emitted by accelerated electric charges. The speed of light is a fundamental physical constant.
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25. A wave front is a surface of constant phase; wave fronts move with a speed equal to the propagation speed of the wave. A ray is a line along the direction of propagation, perpendicular to the wave fronts. Representation of light by rays is the basis of geometric optics.
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26. When light is transmitted from one material to another, the frequency of the light is unchanged, but the wavelength and wave speed can change. The index of refraction n of a material is the ratio of the speed of light in vacuum c to the speed v in the material. If λ0 is the wavelength in a vacuum, the same wave has a shorter wavelength λ in a medium with index of refraction n. (See Example 33.2)
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27. At a smooth interface between two optical materials, the incident, reflected, and refracted rays and the normal to the interface all lie in a single plane called the plane of incidence. The law of reflection states that the angles of incidence and reflection are equal. The law of refraction relates the angles of incidence and refraction to the indices of refraction of the materials. Angles of incidence, reflection, and refraction are always measured from the normal to the surface. (See Examples 33.1 and 33.3)
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28. When a ray travels in a material of greater index of refraction na toward a material of smaller index nb, total internal reflection occurs at the interface when the angle of incidence exceeds a critical angle ncrit. (See Example 33.4)
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29. The variation of index of refraction n with wavelength λis called dispersion. Usually, n decreases with increasingλ.
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30. The direction of polarization of a linearly polarized electromagnetic wave is the direction of the E- field. A polarizing filter used as an analyzer, the intensity Imax of the light transmitted through the analyzer depends on the angle φbetween the polarization direction of the incident light and the polarizing axis of the analyzer. (See Example 33.5)
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31. When unpolarized light strikes an interface between two materials, Brewster’s law states that the reflected light is completely polarized perpendicular to the plane of incidence (parallel to the interface) if the angle of incidence equals the polarizing angle . (See Example 33.6)
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32. Light is scattered by air molecules
Light is scattered by air molecules. The scattered light is partially polarized.
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33. Huygens’ principle states that if the position of a wave front at one instant is known, the position of the front at a later time can be constructed by imagining the front as a source of secondary wavelets. Huygens’ principle can by used to derive the laws of reflection and refraction.
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