Answer:
500 nm, 530 nm, 650 nm
Explanation:
Let's say that there is diffraction grating observed with a slit spacing of s. Respectively we must determine the angle θ which will help us determine the 3 wavelengths ( λ ) of the light emitted by element X. This can be done applying the following formulas,
s( sin θ ) = m λ, such that y = L( tan θ ) - where y = positioning, or the distance of the first - order maxima, and L = constant, of 77 cm
Now the grating has a slit spacing of -
s = 1 / N = 1 / 1200 = 0.833 10⁻³ mm
The diffraction angles of the " positionings " should thus be -
θ = tan⁻¹ ( 0.58 / 0.77 ) = 37°,
θ = tan⁻¹ ( 0.654 / 0.77 ) = 40°,
θ = tan⁻¹ ( 0.945 / 0.77 ) = 51°
The wavelengths of these three bright fringes should thus be calculated through the formula : λ = s( sin θ ) -
λ = 0.833 10⁻³ sin( 37° ) = ( 500 10⁻⁹ m )
λ = 0.833 10⁻³ sin( 40° ) = ( 530 10⁻⁹ m )
λ = 0.833 10⁻³ sin( 51° ) = ( 650 10⁻⁹ m )
Wavelengths : 500 nm, 530 nm, 650 nm