05 refraction of light
- 2. • Although light travels in straight lines, it bends when it passes from one medium to another • Refraction: the bending of light rays as they pass between two different media WHAT IS REFRACTION?
- 3. • Refraction occurs due to changes in the speed of light in different mediums • Different media slow down light by different amounts • The more that light slows down, the more the light is refracted WHY DOES REFRACTION OCCUR?
- 4. • When travelling at an angle towards the muddy surface, one front wheel slows down while the other wheels continue to move at a higher speed. • This causes the path to bend WHY DOES REFRACTION OCCUR?
- 5. WHY DOES REFRACTION OCCUR?
- 7. • Light will follow the path that takes the least amount of time • In a single medium, the pathway is always a straight line • When travelling from one medium to another the fastest pathway is not a straight line • Which path from A to B is faster? FERMAT’S PRINCIPLE
- 8. • Refracted ray: ray of light that is bent when entering a second medium • Angle of refraction: angle between the normal and refracted ray ANGLE OF REFRACTION
- 9. • When travelling from a less dense medium to a more dense medium, light bends towards the normal • When travelling from a more dense medium to a less dense medium, light bends away from the normal ANGLE OF REFRACTION
- 10. • The amount by which a transparent medium decreases the speed of light • Speed of light in a vacuum: 3.0 x 108 m/s • The speed of light changes depending on the medium • Index of refraction is easier system for describing relative speeds INDEX OF REFRACTION Speed of light in a vacuum = 3.00x108m/s Speed of light in water = 2.26x108m/s Speed of light in acrylic = 1.76x108m/s
- 11. • No units: they cancel! or INDEX OF REFRACTION Index of refraction Speed of light in a vacuum (3.00x108m/s) Speed of light in the medium (ex. Water 2.26x108m/s)
- 13. Given: Speed of light in glass = 1.91 x 108 m/s Speed of light in vacuum = 3.00 x 108 m/s = 1.57= 3.00 x 108 m/s 1.91 x 108 m/s .: The refractive index is 1.57 INDEX OF REFRACTION
- 14. v = 2.26 x 108 m/s 1.33 = 3.00 x 108 m/s v .: The speed of light in water is 2.26 x 108 m/s INDEX OF REFRACTION Given: Refractive index in water = 1.33 Speed of light in a vacuum = 3.00 x 108 m/s
- 15. • Dispersion: the refraction of white light into separate wavelengths (colours) • The amount of refraction is different for each colour • Different colours of light travel at different speeds so each refracts a different amount • RRR (Red Refracts Rotten) • BBB (Blue Bends Best) DISPERSION
- 16. DISPERSION
- 17. DISPERSION
- 18. •Materials: • Laser level • Plastic block • White board • Marker •Procedure: 1. Shine the laser on one side of the block. Observe the incident and refracted rays at different angles of incidence 2. Draw 1 incident ray on one side of the block (IR1) 3. Shine the incident ray along IR1. Mark the ray that emerges from the other side as refracted ray 2 (RR2) 4. Connect IR1 with RR2 inside the block with straight lines OBSERVING AND TRACING REFRACTION ACTIVITY
- 19. •Analysis: • Label what you think is refracted ray 1 (RR1) and incident ray 2 (IR2) • Draw a normal on both surfaces of the block • Measure i1, R1, i2, R2 • What do you notice about i1, R2? How about i2, R1? OBSERVING AND TRACING REFRACTION ACTIVITY
- 20. • There is a relationship between the angles of incidence and refraction of the indices of refraction of 2 media (n) • Snell’s Law applies to refraction of light in any situation regardless of the media 2211 sinsin nn SNELL’S LAW
- 21. 1. Light passes from air (n = 1.00) into diamond (n = 2.42) with an angle of incidence of 60.0 degrees. What is the angle of refraction? 2. What is the index of refraction of a material if the angle of incidence in air is 50.0 degrees and the angle of refraction in the material is 40.0 degrees? 3. A diamond ring is dropped into water. The index of refraction for diamond is 2.42. If light strikes the diamond at an angle of incidence of 60.0 degrees, what will be the angle of refraction in diamond? SNELL’S LAW QUESTIONS