Question

Light of wavelength 520 nm is shown through two slits separated by 0.5 mm. The light strikes a screen 1.2 m away, creating a pattern of bright fringes.



a) what is y, the distance between two adjacent bright fringes?



b) the double slit is replaced with a single slit with a width of 0.5 mm. What is the distance to the second dark fringe away from the central maximum?

Answer 1

• In double slit experiment the distance between two bright finges is known as fringe width and is  equal to

 b= lamda . D / d

where  lamda is wavelength and D is the dist from the screen and d is distance b/w the slits

so ATQ,

b=520x1.2x10^-6/0.5

and hence calculate

• for single slit the second dark fringe will be at y=2lamda D/d  
• and the central max will be at the origin therefore the ditance of second dark fringe will be = to y and hence we calulate it by putting in the values