Question

• In the experiment with Newtons ring using reflected light the diameter of the 5th dark ring is 0,336 cm and that of the 15th dark ring is 0.590 cm If the radius of curvature of the plano-convex lens is 99.83 cm. Calculate the wavelength of light used​

Answer 1

Answer:

Given info : In a Newton's rings experiment the diameter of the 15th ring was found to be 0.590 cm and that of the 5th ring was 0.336 cm. If the radius of the plano-convex lens is 100cm.

To find : the wavelength of light used.

Solution : using formula, \lambda=\frac{D_{n+m}^2-D_n^2}{4mR}λ=

4mR

D

n+m

2

−D

n

2

Here diameter of 15th ring, D_{n+m}D

n+m

= 0.59 cm = 5.9 × 10¯³ m

diameter of 5th ring, D_nD

n

= 0.336 cm = 3.36 × 10¯³ m

Here, m = 15 - 5 = 10

R = 100 cm = 1 m

So, wavelength, λ = [(5.9 × 10¯³)² - (3.36 × 10¯³)²]/4 × 10 × 1

= {(34.81 - 11.2896)/40} × 10¯⁶

= 23.5204/40 × 10¯⁶

= 0.5880 × 10¯⁶ m

= 5880 A°

Therefore the wavelength of light used is 5880 A°