refraction
DESCRIPTION
Refraction. Thin Lenses. What Is Love Light?. Isaac Newton believed light to be a ray of corpuscles (particles ), because light travels in a straight line (think inertia!). Robert Hooke believed light to have the wave-like nature. - PowerPoint PPT PresentationTRANSCRIPT
THIN LENSESRefraction
What Is Love Light?
Isaac Newton believed light to be a ray of corpuscles (particles), because light travels in a straight line (think inertia!)
Robert Hooke believed light to have the wave-like nature
Newton’s idea prevailed… until over a century after his death…
LIGHT INTERFERES thus it’s a WAVE!
1801 – Thomas Young produces interference of light
Speed of light is finite, constant…
In vacuum, that is…Light is a(n) ______________ waveIt ____________ a medium
In any substance (anything other than vacuum) light slows down… and its rays bend
Light travels through materials at a speed less than its speed in vacuum.
DEFINITION OF THE INDEX OF REFRACTION
The index of refraction of a material is the ratio of the speed of light in a vacuum to the speed of light in the material:
vcn
material in thelight of Speedin vacuumlight of Speed
nr > ni (faster to slower!)
nr < ni (slower to faster)
SNELL’S LAW OF REFRACTION
When light travels from a material withone index of refraction to a material witha different index of refraction, the angleof incidence is related to the angle ofrefraction by
2211 sinsin nn
SNELL’S LAW
Example 1 Determining the Angle of Refraction
A light ray strikes an air/water surface at anangle of 46 degrees with respect to thenormal. Find the angle of refraction whenthe direction of the ray is (a) from air towater and (b) from water to air.
54.033.1
46sin00.1sinsin2
112
nn 332
96.000.1
46sin33.1sinsin2
112
nn 742
LAB
Determine the index of refraction of a certain plastic
Materials:
Internal Reflection
When light passes from a medium of larger refractive index into oneof smaller refractive index, the refracted ray bends away from the normal.
Critical angle21
1
2 sin nnnn
c
Find critical angle for
1) diamond2) water3) ice
LAB 2
Calculate critical angle and check it experimentally
Materials: