Answer:
615 nm
Step-by-step explanation:
The separation between the two slits, d = 0.195 mm =

The bright interference fringes on the screen are separated by 1.61 cm,

Distance between the screen and the slit, D = 5.1 m
We need to find the wavelength of the laser light. The separation between two bright interference fringes is given by:

So, the wavelength of the laser light is 615 nm.