Answer:
The wavelength is

The frequency is

Step-by-step explanation:
Given that,
Distance between slits d= 0.044 mm
Distance between fringe and center of the pattern y= 8.1 cm
Distance between slits and fringes D = 6.40 m
We need to calculate the wavelength
For constructive interference




Put the value into the formula


We need to calculate the frequency
Using formula of frequency



Hence, The wavelength is

The frequency is
