Newton's ring are formed using light of wavelength 5896A in reflected light eith a liquid placed between the plate and the curved surface.The diameter of the 7th bright fringe is 0.4cm and radiusof curvature is 7m.Find the R.I. of the liquid. plz solve.Thank you.
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Answer: =0.5646×10
−6
=5636
A
o
.
Explanation:
Diameter of the 20th dark ring.
D
20
=5.8 mm=5.82×10
−3
m
Radius of the 20th dark ring
r
20
=2.91×10
−3
m
Diameter of the 10th dark ring
D
10
=3.36 mm=3.36×10
−3
m
Radius of the 10th dark ring
r
10
=1.68×10
−3
m
Radius of plano-convex lens (R)=1 m
Wavelength of light
=
mR
r
n+m
2
−r
n
2
=
10×1
[(2.91×10
−3
)
2
−(1.68×10
−3
)
2
]
=
10
[8.4681−2.8224]×10
−6
=0.5646×10
−6
=5636
A
o
.
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