Page 133 - Physics - XII

Procedure

1. Take a hollow glass prism fi lled with water and tightes the cap at hole, so that water cannot come out
from the hole.
2. With the help of drawing pins, fi x a white sheet of paper on the drawing board.
3. By using a sharp pencil, draw a straight line XX' nearly at the centre of the paper and parallel to the length
of the paper.

4. On the line XX' mark points O , O , O ..... at the suitable distances (about 5 or 6 cm) and draw normals
2
1
3
N O , N O , N O ..... on points O , O , O , ..... as shown in Fig. 5.2.
3
2
3
1
1
2
2
3
1
5. Draw straight lines T O , T O , T O ..... making angles of 30°, 35°, 40°, ..... 60° with the normals N O ,
1
1
3
2
1
2
1
3
N O , N O ..... respectively using a protractor.
3
3
2
2
6. Place the hollow prism fi lled with water on the line XX' and Point O in the middle of the prism. Mark
1
the boundary of the prism ABC as shown in Fig. 5.2.
7. Fix two pins P and Q vertically on the line T O (incident ray line). The distance between the pins
1
1
1
1
should be about 10 to 12 cm. Now, view the images of P and Q through the face AC of the prism.
1
1
Keeping one eye closed and bring open eye in the line of the two images of P and Q . Fix two pins R 1
1
1
and S on the paper vertically and about 10 to 12 cm apart such that the tips of these pins and the tips
1
of the images of the incident ray pins P and Q , all lie on the same straight line.
1
1
8. Remove the pins P , Q and R , S and encircle their pin pricks on the paper sheet with the help of a
1
1
1
1
pencil.
9. Join the pin pricks R and S and produce it backwards to meet the incident ray T O produced (as
1
1
1
1
shown by dotted line in Fig. 5.2). R S is the emergent ray corresponding to the incident ray T O . Mark
1
1 1
1
arrow heads to show the direction of incident and emergent rays.
10. Measure the angle E F S with the help of the protractor. This gives the angle of deviation D .
1 1
1
1
11. Repeat the steps 6 to 10 for diff erent values of angle of incident and measure the corresponding angle
of deviation. Take the values of angle of incidence ranging from 30°, 35°, 40°, 45°, 50°, 55°, and 60°.
12. Repeat the experiment by fi lling diff erent transparent liquids in hollow glass prism.
13. Record all the observations in the observation table.
T 1
N
1 T N 2 T N 3 N 4
P 1 2 3 T
30° P 2 35° P 3 4 P 4
Q 1 O Q 40° 45°
X B 1 F A B 2 O 2 F A B Q 3 O 3 F 3 A B Q 4 F O 4 A X′
1
D 2 4 D
1 4 E
D D 4
R 1 R 2 R 3 R 4
C C 2 C 3 E 3 C S 4
S 1 E S 2 S 3
1 E 2
Fig. 5.2: Refraction through prism at diff erent angles of incidence
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