Solved Numerical Problem No.3 ( Unit-9: Physical Optics); HSSC-1 (Class-11); Physics (New Book/KPK Text Board, Peshawar) With Verified Answers

When the movable mirror of a Michelson interferometer is moved 0.1 mm. How many dark fringes pass through the reference point, if the light of wavelength 580 nm is used? (Ans. 345 fringes)

Given:

Distance moved = P = 0.1 mm = 1 ｘ 10⁻¹ｘ 10⁻³ m = 1 ｘ  10⁻⁴ m

Wavelength of light = λ = 580 nm = 580 ｘ 10⁻⁹ m

To Find:

The number of fringes = m =  ?

Solution:

The formula for the total distance P is

P = m`\frac {λ}{2}`

or

m = `\frac {2P}{λ}`

by putting values

m = `\frac {2 ｘ 1 ｘ 10⁻⁴ m}{580 ｘ 10⁻⁹ m}`

m =  0.00345 ｘ 10⁻⁴⁺⁹

m =  0.00345 ｘ 10⁵

or

m =  345 ｘ 10⁻⁵ ｘ 10⁵

or

m =  345 fringes -------------Ans.

Similar Questions:

A monochromatic light of wavelength 588 nm is allowed to fall on the half silvered plate G1, in the Michelson interferometer. If mirror M1 is moved through 0.233 mm, how many fringes will be observed to shift? (Ans: 792)

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