Question

2.DVD players use red lasers with a wavelength of 650 nm, while Blu-ray players use blue lasers (hence the name) with a wavelength of 405 nm.

1. Which color would need a larger double slit spacing d to produce an interference pattern that has the first maxima 1 mm from the central bright spot?

Answer 1

Blue light

Step-by-step explanation:

For maxima interference we have the relation

`dsin\theta=m`

where

m = order

d = Slit gap

we have the relation

`(dy)/(D)=\lambda`

y = First maxima = 1 mm (fixed)

D = Distance to screen = 1 m (fixed)

So, the wavelength
`(\lambda)` needed should be larger.

Hence, the blue light which has higher wavelength of 650 nm is to be used as it requires larger double slit spacing.