Which of the following equation is used for the constructive interference in optical grating?
A
a cotα=nλ
B
a secα=nλ
C
a tanα=nλ
D
a sinα=nλ
Answer:
The correct option is D. a sinα=nλ
Note
This equation gives the conditions under which constructive interference occurs and relates the spacing of the grating to the light wavelength and the diffraction order, n. Hence, depending on the value of a sinα, one or more diffraction orders, corresponding to n=1,2, etc, may be observed.