Answer:
540 nm
Explanation:
According to the question,
The refractive index of the soap bubble, [tex]n=1.35[/tex].
The thickness of the soap bubble wall is, [tex]t=300 nm[/tex].
Now, for constructive interference of soap bubble.
[tex]2nt=(m+\frac{1}{2})\lambda[/tex].
Now for first order m=1.
Therfore,
[tex]\lambda =\frac{4}{3} tn[/tex]
Substitute all the variables in the above equation.
[tex]\lambda =\frac{4}{3} (1.35)(300 nm)[/tex].
Therefore,
[tex]\lambda =540 nm[/tex].
Therefore the visible light wavelength which is strongly reflected is 540 nm.