Question

I want the right answer it is my thired time to post it?? answer 3.6 and 018 not correct

Light from a sodium lamp (lambda = 589 nm) illuminates a narrow slit and is observed on a screen 77.0 cm behind the slit. The distance between the first and third dark fringes is 2.50 mm Part A What is the width (in mm) of the slit?

Answer 1

Here ,

D = 77 cm = 0.77 m

wavelength = 589 nm

for the width of slit

for the distance between dark fringes

(2.50 - 1) * 10^-3 = 2 * 589 *10^-9 * 0.77/d

solving for d

d = 0.605 mm

the slit width is 0.605 mm