Plz help me with is thank you
A.40.0 km/hr
B.48.6km/hr
C.50.0km/hr
D.53.3km/hr

714 nm

Explanation:

Using the equation: nλ=dsinθ

where

n= order of maximum

λ= wavelength

d= distance between lines on diffraction grating

θ= angle

n is 1 because the problem states the light forms 1st order bright band

λ is unknown

d=   or 0.0000014 (meters)

sin(30)= 0.5

so

(1)λ=(0.0000014)(0.5)

=0.000000714m or 714 nm