Question

Newton’s rings are observed with a plano-convex lens in contact with a glass plate. The radius of the first ring is 1 mm. If the radius of the convex surface is 4 meters, what is the wavelength of light used (in A.U.)?

A. 400 nm
B. 500 nm
C. 600 nm
D. 700 nm

Answer 1

The formula for Newton's rings is used to calculate the wavelength of light used. The correct answer is not listed among the options provided.

Step-by-step explanation:

In Newton's rings experiment, the radius of the first ring is given as 1 mm and the radius of the convex surface is given as 4 meters. We can use the formula for the radius of the nth ring:

rn = √(nλR)

Here, λ is the wavelength of light, R is the radius of curvature of the convex surface, and n is the order of the ring. We can rearrange the equation to solve for λ:

λ = (rn2) / (nR)

Substituting the values 1 mm for rn and 4 meters for R, and considering that the first ring has n = 1, we can calculate the wavelength of light used:

λ = (0.0012) / (1 * 4)

λ ≈ 0.0000025 meters ≈ 2.5 nm

Therefore, the wavelength of light used is approximately 2.5 nm, so the correct answer is not listed.