REFRACTIVE INDEX OF PRISM USING A SPECTROMETER
AIM:- To determine the refractive index of the material of a given prism using a spectrometer.
APPARATUS:- A spectrometer, a spirit level, a source of monochromatic light (sodium vapour lamp), a glass prism, a magnifying lens and a reading lamp.
Theory:- When a beam of light strikes on the surface of transparent material (glass, water, quartz crystal, etc.), the portion of the light is transmitted and and other portion is reflected. The transmitted light ray has small deviation of the path from the incident angle. This is called refraction. Refraction is due to the change in speed of light while passing through the medium. It is given by snell’s law
where i is the angle of incident, r is the angle of refraction, n1 is the refractive index of the first medium and n2 is the refractive index of the second medium.
To determine the angle of the Prism:
Make coincide the slit with the cross wire using fine angle adjusting slider. Then note the reading in the tabular coloumn. Move the telescope in the opposite direction and do the same. Find the difference between two angle ie 2θ.
OBSERVATION:- Write down the actual readings taken upon the apparatus.Take at least three readings of each observation and record them in tabular form as far as possible. Avoid overwriting. This part of the record of the experiment is very important and hence should be written clearly and carefully.
CALCULATION:- Write down the formula to be used and substitute the values obtained to calculate the result. Simplification should be done on the left page. Do logarithmic calculation.
RESULTS:- Write clearly the actual result obtained from your observations.
PRECAUTIONS AND SOURCES OF ERRORS:- Give the precautions taken when conducting the experiment. Discuss the reasons for not getting standard results.
EXPERIMENTAL RESULTS(Approx):-
(1) Angle of Prism = 60°
(2) Angle of Minimum Deviation = 37.2° (degrees).
(3) Refractive Index Of Prism = 1.5
