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Dr. J. C. Bose. On the Influence of the Thickness of
In the next series of observations, the rays were refracted from air into glass. The electric beam was rendered parallel with the help of a glass lens (f = 4 cm.). The beam was incident on the plane face of the semi-cylinder. As the cylinder itself focussed the refracted beam, the objective hitherto used in conjunction with the receiver was dispensed with.
| i. | r. | Mean value of r. | μ. |
| 40° | 18° 19 18 |
18° 20′ | 2·04 |
| 50° | 22° 23 22° 30′ |
22° 30′ | 2·00 |
| 65° | 25° 30′ 26° 27 |
26° 10′ | 2·05 |
Mean value of μ = 2·03 ........ (4).
The different values of μ obtained are given below:—
| From total reflection from a single semi-cylinder, | 2·08 | .... | (1) |
| „„„two semi-cylinders.. | 2·04 | .... | (2) |
| From refraction from glass into air........ | 2·04 | .... | (3). |
| „„air into glass........ | 2·03 | .... | (4) |
The frequency of vibration was of the order 1010.
The value of the optical index of the glass determined by the total reflection method was found to be
μᴅ = 1·53.
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