ICSE Class 10 Answered
Question : a) How does the angle of deviation produced by a prism change with increase in the angle of incidence. Draw a curve showing the variation in the angle of deviation with the angle of incidence at a prism surface.
b) Using the curve in part (a) above, how do you infer that for given prism, the angle of minimum deviation δmin is unique for the given light.
Solution: -
a) As the angle of incidence increases, the angle of deviation decreases first and reaches to a minimum value (δm) for a certain angle of incidence. By further increasing the angle of incidence, the angle of deviation is found to increase.
Variation of angle of deviation (δ) with angle of incidence(i):
b) For a given prism and given colour of light, angle of minimum deviation is unique since only one horizontal line can be drawn parallel to the i-axis at the lowest point of i-δ curve.