Question

In a Young’s double slit experiment, 16 fringes are observed in a certain segment of the screen when light of a wavelength 700 nm is used. If the wavelength of light is changed to 400 nm, the number of fringes observed in the same segment of the screen would be

(1) 28 

(2) 24 

(3) 30 

(4) 18

Answer 1

Answer is (1) 28

N₁λ₁ = N₂λ₂

16 × 700 = N₂ × 400 

⇒ N₂ = 28

Answer 2

Just use this formula and solve

N1λ1 = N2λ2

16 × 700 = N2 × 400

 ⇒ N2 = 28

Comments

Can u give the derivation of this formula