Question

determine the angle of minimum deviation produced in light Ray by a glass prism by plotting graph ​

Answer 1

Refractive index of the material is

$n=\frac{sin(\frac{A+D_{m}}{2})}{sin(\frac{A}{2})}$

Where $D_{m}$ angle of minimum deviation and A is the angle of the prism.

Explanation:

Required Materials  are given below

• Office pins

• Protractor
• Graph paper
• A drawing board
• A white sheet of paper
• A prism
• Drawing pins
• Pencil
• A half-meter scale

Theory

Refraction takes place when light travels from one medium to another medium, because of different medium-light deviate from there path either towards the normal or away from the normal . deviation of light depends on the refractive index of the material .

$n=\frac{sin(\frac{A+D_{m}}{2})}{sin(\frac{A}{2})}$

Where $D_{m}$ angle of minimum deviation and A is the angle of the prism.

Procedure

• Place the white sheet of paper on the drawing board and fix it with the help of drawing pins.

• XX’ is the straight line which is drawn parallel to the length of the paper such that it is in the middle of the paper.

• Mark points $Q_{1},Q_{2},Q_{3}$…… on the straight line XX’ at a distance of 5 cm each.
• $N_{1}Q_{1} and N_{2}Q_{2}$… are the normals that are drawn on the points $Q_{1},Q_{2}$,… as shown in the ray diagram.
• Make angles of 35°, 40°,….,60° by drawing straight lines $R_{1}Q_{1} and R_{2}Q_{2}$,…….. With respect to the normals.

• To take one edge of the prism for all the observation, mark any corner of the prism as A.
• Place the prism with its refracting face AB on the line XX’ and on the point Q1 and also in the middle of AB.Mark the boundary of the prism.
• On the line, $R_{1}$$Q_{1}$, fix office pins vertically and mark them as $P_{1} and P_{2}$ the distance between these pins should not be less than 10mm.

• Through prism face, AC, look for the images of the points $P_{1} and P_{2}$
• Close your left eye and with the right eye open bring it in line with the two images.

• Fix the other two office pins vertically and name them as $P_{3} and P_{4}$ These pins should be 10cm apart from each other. $P_{3}$ and $P_{4}$ should be in one straight with respect to the images of $P_{1}$ and $P_{2}$.

• Encircle the pricks of pins $P_{3}$ and $P_{4}$.
• For points, Q2, Q3,…. for angle 40°, 45°,…..60°, repeat the steps 7 to 13