2021 CAIE AS & A level February March Physics Paper 12 Q. No. 29 (9702/12/F/M/21) by Sajit C Shakya

2021 CAIE AS & A level February March Physics Paper 12 Q. No. 29 (9702/12/F/M/21) by Sajit Chandra Shakya from Nepal Chapter - SUPERPOSITION A beam of red laser light of wavelength 633 nm is incident normally on a diffraction grating with 600 lines per mm. The beam of red light is now replaced by a beam of blue laser light of wavelength 445 nm. A replacement diffraction grating is used so that the first-order maximum of the blue light appears at the same position on the screen as the first-order maximum of the red light from the original laser. How many lines per mm are there in the replacement diffraction grating? A 420 mm–1 B 470 mm–1 C 600 mm–1 D 850 mm–1