Value of theta of first minimum

[desmond iking]

Homework Statement

A parallel beam of monochromatic light of wavelength 580nm is incidentally normal on a diffraction grating. The separation between successive lines on the grating is 0.7μm as shown in the figure.
please refer to the photo , i am having problem with part (a)

Homework Equations

The Attempt at a Solution

my working is d sin θ = λ
sin θ = λ /d , where d is the separation between slits.. by plug in value of λ = 580x10^-9 and d = 1/ (5000x10^2) , i have my θ = 47 ° , the ans given is 56°
why am i wrong?

 

[NascentOxygen]

Where are you given that value for d?

 

[desmond iking]

Where are you given that value for d?

sorry i made a typo.
here's what i mean :
sin θ = λ /d , where d is the separation between slits.. by plug in value of λ = 580x10^-9 and d = 0.7x10^-6 , i have my θ = 47 ° , the ans given is 56°

 

[BvU]

Part a asks about a single slit !
And the distance between slits is NOT 70 micrometer.