KCET2010PhysicsWave Optics
Red light of wavelength 625 ~nm is incident normally on an optical diffraction grating with 2 10⁵ lines / m . Including central principal maxima, how many maxima may be observed on a screen which is far from the grating?
Options
- A15
- B17
- C8
- D16
Correct answer
B. 17
Step-by-step solution
For principal maxima in grating spectra N = n where, n =(1,2,3) is the order of principal maxima and is the angle of diffraction. n = 1 N = 1 6.25 10⁻⁷ 2 10⁵ =8 Number of maxima =2 n +1=2 8+1=17