PHYSICS PRACTICAL FILE
ICSE 2023
INSTRUCTIONS FOR
 FORMATTING
 MATERIAL
& TOPIC
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Today’s Practical Work
EXPERIMENT NO. 3
AIM : Experimental verification of Snell’s Law and
hence to find refractive index( R.I.) of glass
2
Copy information given in slide no. (4 – 8 )
INDEX
EXPERIMET
NO.
3
EXPERIMENT
NAME
DATE
TEACHER’S
SIGNATURE
1
Verification of Ohm’s Law
----
-------
2
Measurement of the mass of a metre
rule
-----
--------
3
Verification of Snell’s Law
& to find R.I.
?
--------
EXPERIMENT NO : 3
DATE : ?.07.2022
 AIM : Verification of Snell’s law & hence to find the refractive index ( R.I. )
of glass
 THEORY :
According to Snell’s law of refraction,
1. The incident ray, refracted ray and the normal at the point of incidence all lie in the same
plane.
2. The ratio of sine of the angle of incidence ( i ) to sine of the angle of refraction ( r ) is
constant for a given pair of media and for a fixed colour of light. i.e, µ = sin i / sin r
= constant .This constant is called R.I. of 2nd medium w. r. to 1st medium.
According to the experiment, R.I. of glass w. r. to air i.e, absolute R.I. of glass material is µg.
In the diagram shown, AO is the incident ray on the glass surface PQ, OB is the
refracted ray in glass, which is further incident at B on glass-air surface SR and finally
refracting in air to produce emergent ray BC , which is parallel to the incident ray AO. The
Angle of incidence at the point of incidence O is ‘ i ‘ and angle of refraction is ‘ r ‘.
( The required diagram given will be drawn by PENCIL at left side white page
adjacent to this page) .
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Diagram
5
6
worksheet to be done in lab (don’t copy it)

OBSERVATION :
No. of
observations
Angle of
Incidence
(i)
1
30 °
2
40 °
3
50 °
Angle of
Refraction
(r)
Value of
sin i
R.I. ( µg )
Value of
sin r
= ( sin i / sin r )
So , mean refractive index ( µg ) = ( ? + ? + ?)/3= ?? .
 RESULT : From the above observations, it is seen that 1. The ratio of ( sin i / sin r) is almost constant for different angles of incidence for
(air – glass) a fixed pair of medium.
2. The incident ray AO, refracted ray OB and the normal NN´ drawn at the point of
incidence O , all lie on the same plane.
So, Snell’s law is verified.
The refractive index of glass ,
7
µg =
?
PRECAUTIONS :
 All pins should be placed vertically.
 The gap between two pins is maintained approx. (3 – 4) cm apart.
 The glass slab must be clean and transparent.
 The glass slab should not be moved throughout the experiment during
pointing the pins to trace out the emergent ray.
 Special care must be taken to measure the angle of incidence and angle
of refracted rays.
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DATE OF SUBMISSION
on the day of this practical in lab
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