Air. Glass. Glass. Air

Transcription

1 ANSWERS INDEX OF REFRACTION The ptical desity f a trasparet medium (material) is a iverse measure f the speed f light thrugh the medium. The mre ptically dese a trasparet medium is, the slwer the speed f light travels i that medium. Remider: The speed f light i a vacuum is 3 x 0 m/s. The speed f light i air is very clse t the speed f light i a vacuum. I this curse, we assume the speed f light i air is c r 3 x 0 m/s. Refracti is the bedig f light rays as they pass frm e medium it ather medium f differet ptical desity. The idex f refracti f a trasparet medium is a rati f the speed f light i a vacuum (air) t the speed f light i the medium: = c/v where = is the idex f refracti ( uits) c = 3 x 0 m/s v = speed f light i the medium (i m/s) Nte: The greater the idex f refracti f a medium, the slwer light travels i that medium. The idex f refracti fr a vacuum is e (), fr water it is.33, fr diamd it is.4, etc. Whe refracti ccurs, light beds away frm the rmal whe the ptical desity (idex f refracti) is less dese (ad vice versa). The fllwig illustrati demstrates this fact: Air Glass Glass Air Refracted ray beds twards rmal. Refracted ray beds away frm rmal. SNELL S LAW Sell s Law describes the relatiship betwee the agle f icidece ad the agle f refracti whe refracti ccurs. Mathematically, Sells s Law is writte as: Si i where = = idex f refracti f medium-e (medium f icidet ray) = idex f refracti f medium-tw (medium f refracted ray) i r = agle f icidece = agle f refracti PHYSICS 534 OPTICS AsPhysics Ex-50.DOC 999 S. Lacie Page /5

2 . Defie refracti ad explai hw it differs frm reflecti. Reflecti is the bedig f light with the icidet ray ad the reflected ray beig i the same medium (there is ly e medium). Refracti is the bedig f light as it passes frm e medium it ather medium (there are tw mediums).. Defie what is meat by the ptical desity f a medium. The ptical desity f a medium refers t the speed f light i that medium. The greater the idex f reacti f a medium, the slwer light travels i that medium. 3. Des the speed f light icrease r decrease as the ptical desity f a medium icreases? Decrease 4. Explai what is meat by the idex f refracti f a medium. The idex f refracti () f a medium is the rati f the speed f light i that medium t the speed f light i a vacuum (3 x 0 m/s). The greater the idex f refracti f a medium, the slwer light travels i that medium. Nte that the idex f refracti has uits. 5. State Sell s Law. 6. What is the purpse f Sell s Law? The purpse f Sell s Law is t calculate the agle f refracti give the agle f icidece. Or, cversely, t calculate the agle f icidece give the agle f refracti. PHYSICS 534 OPTICS AsPhysics Ex-50.DOC Law f Refracti Part- / Page /5

3 7. The speed f light i a plexiglas is. x 0 m/s. Calculate the idex f refracti fr this plexiglas. [.43] c v. 0. The diagrams belw illustrate a ray f light travelig frm e medium t ather. I the first case, light travels frm a lesser t a greater desity medium (air t glass). I the secd case, light travels frm a deser t a less dese medium (glass t air). Draw the refracted ray fr each case. 9. A ray f light eters a trasparet material at a agle f icidece f 45. If the agle f refracti is, what is the idex f refracti f the substace? [.5] Draw the refracted ray. Si i Si r Si i ()(Si 45 ).5 Si 0. Kwig that the idex f refracti fr diamd is.4, calculate the speed f light i diamd. [. x 0 m/s] c v c 3 0 v. 0.4 PHYSICS 534 OPTICS AsPhysics Ex-50.DOC Law f Refracti Part- / Page 3 /5

4 . A ray f light eters water at a agle f icidece f 30. The agle f refracti is fud t be. Calculate the idex f refracti fr water. [.33] Si i ()(Si 30 ).33 Si r Si. I travelig frm air it water, a ray f light makes a agle f icidece f 5. Calculate the agle f refracti. [36 ] Si i ()(Si 5 ) r Frm previus prblem 3. I travelig frm water it air, a ray f light makes a agle f refracti f 59. Calculate the agle f icidece. [40 ] ()(Si 59 ) Si i i A ray f light emerges frm water it air with a agle f icidece f. What is the agle f refracti? [30 ] Si i (.33)(Si ) 0.49 r PHYSICS 534 OPTICS AsPhysics Ex-50.DOC Law f Refracti Part- / Page 4 /5

5 5. The idex f refracti f flit glass is.63. Fid the agle f icidece fr a ray f light eterig flit glass frm air such that the agle f refracti is 35. [69 ] (.63)(Si 53 ) Si i i A light ray passes thrugh tw liquids, e flatig tp f the ther, i a beaker. The agle f refracti i the water is 5. Determie the agle f icidece (A ). [34 ] A Air ( =.0) Oil ( =.46) 5 Water ( =.33) Oil Water (.33)(Si 5 ) Si i i.6.46 Water Oil (.46)(Si.6 ) Si i i PHYSICS 534 OPTICS AsPhysics Ex-50.DOC Law f Refracti Part- / Page 5 /5