Advertisements
Advertisements
Question
Plot a graph to show the variation of the angle of deviation as a function of the angle of incidence for light passing through a prism. Derive an expression for the refractive index of the prism in terms of angle of minimum deviation and angle of the prism.
Solution
If the angle of incidence is increased gradually, then the angle of deviation first decreases, attains a minimum value (δm) and then again starts increasing.
When the angle of deviation is minimum, the prism is said to be placed in the minimum deviation position.
There is only one angle of incidence for which the angle of deviation is minimum.
When δ = δm [prism in minimum deviation position],
e = i and r2 = r1 = r …..(i)
∵ r1+r2=A
From (i), we get
r + r = A
`r=A/2`
Also, we have
A + δ = i + e
Substituting δ = δm and e = i,
A + δm = i + i
`i=(A+delta_m)/2`
∵`mu=sin i/sin r`
`:.mu=(sin(A+delta_m/2)/Sin (A/2))`
RELATED QUESTIONS
A ray of light passes through an equilateral glass prism such that the angle of incidence is equal to the angle of emergence and each of these angles is equal to 3/4 of angle of prism. Find the angle of deviation.
Two monochromatic rays of light are incident normally on the face AB of an isosceles right-angled prism ABC. The refractive indices of the glass prism for the two rays '1' and '2' are respectively 1.38 and 1.52. Trace the path of these rays after entering through the prism.
Draw the ray diagram showing refraction of light through a glass prism and hence obtain the relation between the refractive index μ of the prism, angle of prism and angle of minimum deviation.
Out of blue and red light which is deviated more by a prism? Give reason.
Three thin prisms are combined as shown in figure. The refractive indices of the crown glass for red, yellow and violet rays are μr, μy and μv respectively and those for the flint glass are μ'r, μ'y and μ'v respectively. Find the ratio A'/A for which (a) there is no net angular dispersion, and (b) there is no net deviation in the yellow ray.
A thin prism of crown glass (μr = 1.515, μv = 1.525) and a thin prism of flint glass (μr = 1.612, μv = 1.632) are placed in contact with each other. Their refracting angles are 5.0° each and are similarly directed. Calculate the angular dispersion produced by the combination.
A ray of light is incident on a prism whose refractive index is 1.52 at an angle of 40°. If the angle of emergence is 60°, calculate the angle of the prism.
Calculate dispersive power of a transparent material given : nv = 1.56, nr = 1.54, ny = 1.55.
What is meant by the dispersive power of transparent material?
When a ray of white light is incident obliquely on the first surface of a prism, then ______.
