REFLECTION, REFRACTION & PRISM
Reflection of light -
When a ray of light strikes a polished surface, it bounces back in a particular direction. This is known as reflection of light.
Laws of Reflection -
The laws of reflection can be summarized as :
1. The incident ray, the reflected ray and the normal at the point of incidence, all lies in the same plane.
2. The angle of incidence is equal to the angle of reflection.
Refraction of light -
When a ray of light passes from one medium (say air) to another medium (say glass) of different optical density, it deviates from its original path. This is called refraction.
Laws of Refraction -
1. The incident ray and the refracted ray are on the opposite sides of the normal at the point of incidence and all three lie in the same plane.
2. The ratio of sine of angle of incidence to the Sine of angle of refraction is constant. This is known as snell's law.
Sine angle of incidence or sine angle of refraction ine donon ke ratio ko refractive index Kahate hain.
Prism -
A Prism is a refracting medium bound by two plane surfaces which are inclined at an angle called the apical angle or the refracting angle of the prism.
Uses -
Diagnostic uses
- Objective measurement of angle of deviation
- Measurement of fusional reserve
- Diagnosis of microtropia
Instruments uses
- Applanation tonometer
- Indirect ophthalmoscopes
- Keratometer
- Operating microscope
- Synoptophore
- Haidinger brushes
Therapeutic uses
- Treatment of convergence insufficiency
- Treatment of diplopia
Miscellaneous uses
- Low vision AIDS
- Hemianopic spectacles
- Recumbent spectacles
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