Question

2. A diffraction grating has 300 lines per mm. The grating is used to observe normally incident light with a wavelength of 440 nm. The grating is placed 1.3 m from a screen. Where on the screen will the first order bright line appear?

Answer 1

Condition for maximum d sin theta = m d d rightdoublearrow distance between slits theta = angle for maximum d = wave length = 440 nm m rightarrow order of bright line m = 1 d = 1/300 times 10^-3 = 3 d rightdoublearrow 300 lines/mm so,.spacing 1/300 mm d = 3.33 times 10^-6 m sin theta = 440 times 10^-g/3.33 times 10^-6 sin theta = 0.1321 theta = 7.593 degrees