Question

10.In Newtons ring experiment by reflected light the diameter of the 15th bright ring is 7mm .If the radius of curvature of the planoconvex lens is 100cm and the wavelength of light is 6000AU Calculate the diameter of the 5th bright ring.​

Answer 1

Answer:

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

.

Answer 2

Given:

• Diameter of the 15th ring, $D_{15}$  = 7 mm = 7×$10^{-3}$ m
• The radius of the planoconvex lens = 100 cm = 1m
• The wavelength of light = 6000 Au

To Find:

• The diameter of the 5th bright ring.

Solution:

The formula to find the diameter of the bright ring is given by:

$D_n = \sqrt{2(2n-1)(lambda)R}$

Where 'n' is the order of rings, 'λ' is the wavelength of light, and 'R' is the radius of curvature of the planoconvex lens.

The diameter of the 5th bright ring is given by,

$D_5$ = $\sqrt{2(2*5-1)6000*10^{-10}*1}$  = $\sqrt{108000*10^{-10}}$  = 3.28*$10^{-3}$ m

∴ The diameter of the 5th ring = 3.28×$10^{-3}$