In an experiment with a rectangular glass slab, a student observed that a ray of light incident at an angle of $55^{\circ}$ with the normal on one face of the slab, after refraction strikes the opposite face of the slab before emerging out into air making an angle of $40^{\circ}$ with the normal. Draw a labelled diagram to show the path of this ray.' What value would you assign to the angle of refraction and angle of emergence?
CBSE OUTSIDE DELHI - SET 1 2010
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OA - Incident ray
1 is angle of incidence $=50^{\circ}$
Given $r_2=40^{\circ}$
$r_1$ and $r_2$ are alternate interior angles,
$\therefore \angle r_1=\angle r_2=40^{\circ}
So, angle of refraction $=40^{\circ}$
Since, the emergent ray is parallel to the incidnt ray, the angle of emergent must be equal to angle of incidence, i.e.
$\angle e=\angle i=55^{\circ}$
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