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Physics Class 12
Solutions to CBSE Sample Paper - Physics Class 12

A narrow slit is illuminated by a parallel beam of monochromatic light of wavelength λ equal to 6000 Å and the angular width of the central maximum in the resulting diffraction pattern is measured. When the slit is next illuminated by light of wavelength λ’, the angular width decreases by 30%. Calculate the value of the wavelength λ’.



Angular width 2φ = 2λ/d

Given λ = 6000 Å

In Case of new λ (assumed λ’ here),

angular width decreases by 30%

New angular width = 0.70 (2 φ)

2 λ’/d = 0.70 X (2 λ/d)

∴λ’= 4200 Å

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Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 13 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.