A slit of width mm is illuminated by a beam of light consisting of two wavelengths nm and nm. The diffraction pattern is observed on a screen m from the slit. Find:
(i) the distance of the second bright fringe from the central maximum pertaining to light of nm;
(ii) the least distance from the central maximum at which bright fringes due to both the wavelengths coincide.
(i) the distance of the second bright fringe from the central maximum pertaining to light of nm;
(ii) the least distance from the central maximum at which bright fringes due to both the wavelengths coincide.
Answer: (i) m mm.
(ii) m mm.
Solution
For single-slit diffraction a secondary bright fringe (maximum) of order lies at
(i) Second bright fringe () for nm, with m, m:
(ii) Bright fringes coincide when :
The smallest odd integers in ratio cannot be taken directly; the lowest coincidence is — taking the least common position is at m (where the maximum of nm aligns with a maximum of nm).
(i) Second bright fringe () for nm, with m, m:
(ii) Bright fringes coincide when :
The smallest odd integers in ratio cannot be taken directly; the lowest coincidence is — taking the least common position is at m (where the maximum of nm aligns with a maximum of nm).
CBSE Class 12 Board · Subjective