# White Light

#### Velocity

This question really has me stumped..i would appreciate it if anyone could help me out

White light containing wavelengths of 400nm to 750 nm is shone normally onto a diffraction grating of 3000 lines/cm. Calculate the width of the spectrum that appears as the second antinode on a screen that is 100 cm away.

Is there a specific formula I can use to solve the question? If so then please help.. thanks

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#### eNtRopY

Yes, use the diffractin grating equation.

n lamda = d sin theta

Rearrange the terms, solve for theta for two cases -- the longest wavelength at the n=2-mode and the shortest wavelength at the n=3-mode. Use this information with the distance between the grating and the screen to solve the problem -- just a little trigonometry.

eNtRopY

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