Question

# Two narrow slits are illuminated by a laser with a wavelength of 578 nm. The interference...

Two narrow slits are illuminated by a laser with a wavelength of 578 nm. The interference pattern on a screen located x = 4.50 m away shows that the third-order bright fringe is located y = 9.10 cm away from the central bright fringe. Calculate the distance between the two slits.

 First you have to calculate the angle of the maximum. Then you can use the formula for bright fringes of double slits.
 Incorrect. Tries 2/20 Previous Tries

The screen is now moved 2.4 m further away. What is the new distance between the central and the third-order bright fringe?

The expression of the position of the fringe from the center of the central pattern can be expressed as follows,

Y = m** x/d

d = m*x/Y = 3 *578*10^-9 *4.5 /( 9.1*10^-2)

The distance between the two slit is = d = 8.57472527e-5 m

The screen is now moved 2.4 m

so x' = 2.4 +x = 2.4 +4.5 = 6.9

y' = m** x'/d

= 3*578*10^-9*6.9 / (8.57472527e-5)

y' =0.139533333​ m

The position of the fringe is = 0.139533333​ m

let me know in a comment if there is any problem or doubts

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