physics chp 15
DESCRIPTION
Physics Chp 15. What happens when “light” hits a transparent material?. Some of it reflects and/or refracts Refraction is the bending of light due to a change in it’s speed in the new material. Index of refraction n = c/v 1 or greater. - PowerPoint PPT PresentationTRANSCRIPT
Physics Chp 15
• What happens when “light” hits a transparent material?
• Some of it reflects and/or refracts
• Refraction is the bending of light due to a change in it’s speed in the new material
• Index of refraction
• n = c/v 1 or greater
• While θi=θr for reflection it isn’t always true for refraction, it depends in n
• Snell’s Law
• n1sinθ1 = n2sinθ2
• So why do objects under the water look closer to the surface and farther away from us than they really are?
• Why does “light” refract?
• Lenses use refraction to redirect light
• Converging – brings the light towards the axis
• Diverging – directs the light away from the axis
• Ray Diagrams• Converging• 1 – from tip parallel then towards f• 2 – from tip thru f then parallel • 3 – from tip thru center
• Ray Diagram• Diverging• 1- parallel then away from f• 2- towards far f then parallel• 3 – thru center
• Thin lens equation
• Magnification equation
1 1 1
o id d f
i i
o o
h dmh d
• Signs
• f + converging
• do + on the left of lens
• di + on the right of lens
• m + for upright
• Sketch a ray diagram for a converging lens with focal length of 1 m and the object 0.5 m left of the lens and 0.2 m tall. Then calculate the distance of the image as well as it’s height.
1 1 10.5 1id
10.2 0.5ih
• Multiple Lenses image 1 = object 2
• Eye Type of lense?
• Near point – closest object distance that still gives a clear image
• Far point – farthest object distance that still gives a clear image
• Nearsightedness – far point issue, image in front of retina, use a diverging lens
• Farsightedness – near point issue, image is behind the retina, use a converging lens
• Microscope
• Telescope
• If n1 > n2 then there is an angle where θ2 = 90o
• Sinθc = n2 / n1
• θc is the critical angle
• If θ = θc then the “light” totally internally reflects
• Since each wavelength refracts differently prisms cause the rainbow from white light
• Also rainbows in the sky are caused by water droplets dispersing the light back towards us.
• Lens Aberrations – not a single focal pt
• Spherical aberrations – farther from the principal axis moves the focus
• Chromatic aberrations – different wavelengths refracting differently