Ch30 - Chapter 30: Reflection and Refraction The nature of...

Info iconThis preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 30: Reflection and Refraction The nature of light ± Speed of light (in vacuum) c = 2.99792458 x 10 8 m/s measured but it is now the definition
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Michelson’s 1878 Rotating Mirror Experiment Picture credit German American physicist A.A. Michelson realized, on putting together Foucault’s apparatus, that he could redesign it for much greater accuracy. Instead of Foucault's 60 feet to the far mirror, Michelson used 2,000 feet. . Using this method, Michelson was able to calculate c = 299,792 km/s 20 times more accurate than Foucault Accepted as the most accurate measurement of c for the next 40 years.
Background image of page 2
The nature of light ± Waves, wavefronts, and rays • Wavefront: The locus of all adjacent points at which the phase of vibration of a physical quantity associated with the wave is the same. rays wavefronts source spherical wave plane wave
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Reflection and refraction ± Reflection and refraction • When a light wave strikes a smooth interface of two transparent media (such as air, glass, water etc.), the wave is in general partly reflected and partly refracted (transmitted). incident rays reflected rays a θ r b b b a a refracted rays
Background image of page 4
Reflection and refraction ± Reflection • The incident, reflected, and refracted rays, and the normal to the surface all lie in the same plane. incident rays reflected rays • The angle of reflection is equal to the angle of incidence for all wavelengths and for any pair of material. r θ a a r b b a a r θ= refracted rays
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Reflection and refraction ± Refraction incident rays reflected rays • The index of refraction of an optical material (refractive index), denoted by n, is the ratio of the speed of light c in vacuum to the speed v in the material. n v c n / ; / 0 λ λ= = wavelength in vacuum. Freq. stays the same. a θ r b b • The ratio of the sines of the angles and , where both angles are measured from the normal to the surface, is equal to the inverse ratio of the two indices of refraction: a b a a b b a n n = sin sin Snell’s law refracted rays
Background image of page 6
Total internal reflection ± Total internal reflection , sin sin 2 1 2 1 θ n n = 1 sin 2 = when Since . sin & 1 / 1 1 2 1 2 n n n n = > When this happens, is 90 o and is called critical angle. Furthermore 2 1 when , all the light is reflected (total internal reflection).
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 8
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 30

Ch30 - Chapter 30: Reflection and Refraction The nature of...

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online