Originally Posted by **ling233** please refer to the photo , i am having problem with part (a)
my working is d sin θ = λ
sin θ = λ /d , where d is the seperation between slits.. by plug in value of λ = 580x10^-9 and d =0.7X 10^-6 , i have my θ = 47 ° , the ans given is 56°
why am i wrong? |

Hi,

a) In the picture the wavelength of light is given as 580 mm. It must be 580 nm.

b) You are calculating the first maximum with the formula

sin θ = λ /d

which in general is

sin θ = m λ /d.

Giving

λ = 580x10^-9 and d =0.7X 10^-6

sin θ = 580 x 10^-9 / 0.7 x 10^-6 = 0.83 and

arcsin (0.83) = 56°.

c) I do not understand how the book gives the 16°, 34° and the 56° for the first, second and the third orders. By the way the a) part of the question does not ask the first maximum but the first minumum!