Question

Light of wavelength 600nm in incident normally on a diffraction grating 3cm wide

Answer 1

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Answer 2

Question: Light of wavelength 600 nm is incident normally on a diffraction grating 3.00 cm wide. If second order line is observed at an angle of 30 degree what is the total number of lines on the grating?

As we know in diffraction grating

For dark position

asin\theta = N\lambda

now for 2nd order position

asin\theta =2\lambda

given that

\lambda = 600 nm

and

\theta = 30 degree

now we have

a sin30 =2*600*10^{-9}

a = 2.4*10^{-6} m

now we can write

\frac{d}{N} = 2.4*10^{-6}

\frac{0.03}{N} = 2.4*10^{-6}

N = 12500

so number of lines are 12500