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

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Presentation on theme: "Happyphysics.com Physics Lecture Resources Prof. Mineesh Gulati Head-Physics Wing Happy Model Hr. Sec. School, Udhampur, J&K Website: happyphysics.com."— Presentation transcript:

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

2 Ch 33 The Nature and Propagation of Light © 2005 Pearson Education

3 33.1 The Nature of Light © 2005 Pearson Education Speed of light= x10 8 m/s Wave front: describe wave propagation Source Wave fronts Rays Wave fronts

4 © 2005 Pearson Education Geometric optics: the branch of optics which is used for the ray description. Physical optics: the branch dealing specifically with wave behavior

5 33.2 Reflection and Refraction © 2005 Pearson Education

6 Reflection and Refraction Incident rays Reflected rays Refracted rays Normal θbθb θaθa θrθr © 2005 Pearson Education

7 index of refraction © 2005 Pearson Education Type of reflection

8 law of reflection law of refraction © 2005 Pearson Education

9 wavelength of light in a material © 2005 Pearson Education

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. 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: ANS: © 2005 Pearson Education

11 33.3 Total Internal Reflection critical angle for total internal reflection © 2005 Pearson Education P nbnb nana θaθa θbθb θ crit Θ b =90° >θ crit

12 Application of total internal reflection © 2005 Pearson Education

13 33.4 Dispersion The dependence of wave speed and index of refraction on wavelength is called dispersion The dependence of wave speed and index of refraction on wavelength is called dispersion © 2005 Pearson Education

14 Dispersion of light by a prism

15 © 2005 Pearson Education Rainbow

16 33.5 Polarization © 2005 Pearson Education Polarization is a characteristic of all transverse waves. Polarized in y-direction Polarized in z-direction

17 © 2005 Pearson Education Polarizing filter

18 © 2005 Pearson Education A Polaroid filter is illuminated by unpolarized natural light

19 Maluss law, polarized light passing through an analyzer © 2005 Pearson Education

20 Polarization by reflection Plane of incidence Reflecting surface Normal Natural light Reflected light is 100% polarized perpendicular to the plane of incidence Transmitted light is partially polarized parallel to the place of incidence

21 Brewsters law for the polarizing angle © 2005 Pearson Education

22 33.6 Scatttering of Light © 2005 Pearson Education 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.

23 33.7 huygens Principle © 2005 Pearson Education 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

24 © 2005 Pearson Education 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.

25 © 2005 Pearson Education 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.

26 © 2005 Pearson Education 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 λ 0 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)

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) © 2005 Pearson Education

28 When a ray travels in a material of greater index of refraction n a toward a material of smaller index n b, total internal reflection occurs at the interface when the angle of incidence exceeds a critical angle n crit. (See Example 33.4)

29 © 2005 Pearson Education The variation of index of refraction n with wavelength λis called dispersion. Usually, n decreases with increasingλ.

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 I max 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) © 2005 Pearson Education

31 When unpolarized light strikes an interface between two materials, Brewsters 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)

32 © 2005 Pearson Education Light is scattered by air molecules. The scattered light is partially polarized.

33 © 2005 Pearson Education 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.

34 END Visit: happyphysics.com For Physics Resources


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