Question

A laser of wavelength 720 nm illuminates a double slit where the separation between the slits is 0.22 mm. Fringes are seen on a screen 0.85 m away from the slits. How far apart are the second and third bright fringes

Answer 1

The appropriate solution is "2.78 mm".

Step-by-step explanation:

Given:

`\lambda = 720 \ nm`

or,

`= 720* 10^(-9) \ m`

`D=0.85 \ m`

`d = 0.22 \ mm`

or,

`=0.22 * 10^(-3) \ m`

As we know,

Fringe width is:

⇒
`\beta=(\lambda D)/(d)`

hence,

Separation between second and third bright fringes will be:

⇒
`\theta=\beta=(\lambda D)/(d)`

`=(720* 10^(-9)* 0.85)/(0.22* 10^(-3))`

`=2.78* 10^(-3) \ m`

or,

`=2.78 \ mm`