In an experiment to trace the path of a ray of light through triangular glass prism. a) If the emergent ray makes an angle of 35° with the 2nd face of the prism then what is the angle of emergence? b) can the angle of deviation be zero? Why?
Answers
No, the deviation cannot be zero. This is because of the non parallel faces of the prism.
Angle of incidence = 55°
Explanation:
Prism is a homogeneous, transparent, refracting material (such as glass) enclosed by two inclined plane refracting surfaces at some fixed angle called refracting angle or angle of the prism. When a ray of light falls on prism, it gets refracted. The light that lands on the prism is called the incident ray and the ray that comes out of the other plane of the prism is called the angle of emergence. The angle between the incident ray and the emergent ray is called the angle of deviation.
The angle of deviation decreases as the angle of incidence decreases, only up to a particular point called the minimum angle of deviation of a prism. After that value, the angle of deviation will not decrease further. So angle of deviation cannot be zero, as the two planar surfaces of the prism are not parallel.
Angle of emergence = ∠e = 90° – angle of incidence
When ∠e = 35°, then angle of incidence = 90° – 35° = 55°
Angle of incidence = 55°