Answer:
λ = 6 10⁻⁷ m
Explanation:
This problem is a double slit interference spectrum where bright maxima are described by constructive interference.
d sin θ = m λ
Where d is the gap of the slits (d = 0.2 10⁻³ m), m is the maximum interference and λ is the wavelength
We used trigonometry to find the angle
tan θ = y / x
Since the angles in these experiments are very small we use
tan θ = sin θ / cos θ = sin θ
sin θ = y / x
We substitute
d y / x = m λ
λ = d y / m x
In this case the first maximum is m = 1
We substitute
λ = 0.2 10⁻³ 3.6 10⁻³ / (1 1.2)
λ = 6 10⁻⁷ m
The approximation made in this problem is that since the angles are small we approximate the tangent to the sine
