Question

If wavelength changes by $\Delta \lambda$ then change in propagation vector is:

• A. $\Delta \lambda$
• B. $2\pi \Delta \lambda$
• C. $\frac{2\pi }{\lambda }\Delta \lambda$
• D. $-\frac{2\pi }{{\lambda }^2}\Delta \lambda$

Answer 1

The correct option is D $-\frac{2\pi }{{\lambda }^2}\Delta \lambda$

$k=\frac{2\pi }{\lambda }$ differentiating $dk=\frac{-2\pi }{{\lambda }^2}d\lambda$