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# 2 Refraction Of Light

## on Feb 20, 2010

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## 2 Refraction Of LightPresentation Transcript

•
• REFRACTION OF LIGHT
• A pencil appears bent or broken when it is partially immersed in water
•
• These are two situation that show the effect produced when light travels from one medium to another The effects are due to the change of direction of light when light travels from one medium to another.
•
• Refraction of Light
• Refraction of light is the bending of a light rays at the boundary as the rays travel from one medium to another.
• Light rays bend towards the normal when the rays travel from a less dense medium to a denser medium (eg: water to glass)
• Light rays bend away from the normal as it travels from a denser medium to a less
• dense medium.
•
• less dense denser medium i r i = angle of incidence r = angle of refraction i > r Normal line incident ray refraction ray
• Light rays bend towards the normal when the rays travel from a less dense medium to a denser medium
• Light rays travel much slower in a denser medium
less dense denser medium i r i = angle of incidence r = angle of refraction Normal line incident ray refraction ray air kaca air water
• denser medium less dense i r i = angle of incidence r = angle of refraction i < r Normal line incident ray refraction ray
• Light rays bend away from the normal as it travels from a denser medium to a less dense medium.
• Light rays travel much faster in a less dense medium
denser medium less dense i r i = angle of incidence r = angle of refraction Normal line incident ray refraction ray air glass air water
• When light ray travels from one medium to another, its speed changes. The change in speed of the light ray cause the change of its direction.
• Experiment
• Aim:
• To investigate the relationship between the angle of incidence i and the angle of refraction r.
• Inference:
• The value of sin r is manipulated by the value of sin i
• Hypotesis:
• The greater the value of sin i the greater
• will be the value of sin r.
• Aim:
• To investigate the relationship between the angle of incidence i and the angle of refraction r.
• Inference:
• The value of sin r is manipulated by the value of sin i
• Hypotesis:
• The greater the value of sin i the greater
• will be the value of sin r.
•
•
•
• Refractive Index
• For a light ray travels from vacuum (or air) into a given transparent medium, the ratio of is is always constant.
• Snell’s Law,
• Refraction index, n = Sin i Sin r
•
• Refractive Index
• Laws of Refraction
• 58.7  40  water air 30  19.2  air kaca 60  40.6  water air 75  40.4  perspex air Example 1. 3. 1. 2. 4.
• n = speed of lights in the air @ vacuum
• speed of lights in the medium
Refractive Index and Speed of Light The speed of light in a vacuum is about 3.0 x 10 8 ms -1. Light travels much slower in transparent materials.
• Example
• By applying the principle of reversibility of light, light travelling from point A to point B through any system can also travel from B to A along the same path in the reverse direction.
• n  1
• Sin i  1
• Sin r
• Sin i  Sin r
• i  r