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a.) Exactly four bright fringes are seen on either seide ofthe central maximum w

ID: 1742955 • Letter: A

Question

a.) Exactly four bright fringes are seen on either seide ofthe central maximum when a diffraction grating is illuminated withyellow-green light of wavelength = 570nm. What is the maximumnumber of lines/m for the grating? b) If violet light of frequency 7.9x10^14 Hz is used with thesame grating, what is the highest order maximum that can beseen? a.) Exactly four bright fringes are seen on either seide ofthe central maximum when a diffraction grating is illuminated withyellow-green light of wavelength = 570nm. What is the maximumnumber of lines/m for the grating? b) If violet light of frequency 7.9x10^14 Hz is used with thesame grating, what is the highest order maximum that can beseen?

Explanation / Answer

a) the maximum number of bright fringes that can be seen oneither side of the central maximum occurs when the angle is     = 900 the bright fringes in diffraction grating is given as      dsin = m        or d =m/sin               = 4*570*10-9m / sin900               =2.280*10-6m the number of lines per centimeter is                  N = 1/d                      = 1/2.280*10-6m                      = 438596 lines/m b) frequency is f = 7.9*1014 Hz    so wavelength = c/f                             = 3*108m/s / 7.9*1014 Hz                             = 380*10-9m       we have       dsin = m          m =dsin900 / 380*10-9m               =(2.280*10-6m)*1 / 380*10-9m              = --------------------               =2.280*10-6m the number of lines per centimeter is                  N = 1/d                      = 1/2.280*10-6m                      = 438596 lines/m b) frequency is f = 7.9*1014 Hz    so wavelength = c/f                             = 3*108m/s / 7.9*1014 Hz                             = 380*10-9m       we have       dsin = m          m =dsin900 / 380*10-9m               =(2.280*10-6m)*1 / 380*10-9m              = --------------------