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| Question | Answer |
| What is need for Total Internal Reflection? | 1. Angle of incidence > Critical Angle 2. Light must be passing from a high refractive index to a low one. |
| State 2 uses of Total Internal Reflection | 1. Optical Fibres 2. Prismatic Periscopes |
| What is the equation to identify the critical angle? | |
| What happens at Total Internal Reflection? | A ray hits the boundary of the material at an angle other than 90º and changes direction beyond the critical angle, causing all the rays reflect back into the material |
| What happens when you have a greater refractive index? | The greater the refractive index, the greater the light bends towards the normal |
| What is the critical angle? | The angle of incidence that produces an angle of refraction of 90° |
| Does Total Internal Reflection happen naturally? | No, it is unique and very useful as it is 100% efficient at transferring the light energy. |
| Why do you sometimes get a weak reflection? | The larger the angle of incidence the more of the light is reflected and less of it passes into the other medium. |
| How are optical fibres used for medicinal purposes? | In endoscopy, thousands of optical fibres are bundled together in an endoscope which is inserted into a human body so that the doctor can 'see' inside. Light can be directed down the fibres even if they are bent. |
| Calculate the critical angle from glass to water. (Water = 1.33, Glass = 1.5) | c = 63 sin(c) = n(r)/ n(i) 1. sin(c) = 1.33/1.5 =0.89 2. c = sin-1 (0.89) = 63 |
| Why does a diamond sparkle? | Diamond is the material that gives off the smallest critical angle. Rays of light can easily be made to 'bounce around inside them' by careful cutting of the stone and the refraction at the surfaces splits the light into a spectrum of colours |
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