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Multiple Choice
A diffraction grating with is illuminated by two wavelengths of light: and What is the distance between the bright fringes of the two colors of light on a screen away?
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Verified step by step guidance
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First, understand that a diffraction grating causes light to spread out into its component wavelengths. The formula for the angle of the m-th order bright fringe is given by: \( d \sin \theta = m \lambda \), where \( d \) is the distance between adjacent grating lines, \( \theta \) is the angle of diffraction, \( m \) is the order number, and \( \lambda \) is the wavelength of light.
Calculate the grating spacing \( d \) using the given 500 lines/mm. Convert this to meters: \( d = \frac{1}{500 \times 10^3} \) meters.
For each wavelength, use the formula \( d \sin \theta = m \lambda \) to find the angle \( \theta \) for \( m = 2 \). Start with \( \lambda = 450 \) nm, convert it to meters, and solve for \( \theta \). Repeat the process for \( \lambda = 600 \) nm.
Once you have both angles, use the small angle approximation \( \tan \theta \approx \sin \theta \approx \theta \) (in radians) to find the position \( y \) of each fringe on the screen using \( y = L \tan \theta \), where \( L = 1.3 \) m is the distance to the screen.
Finally, calculate the distance between the two \( m=2 \) bright fringes by finding the difference in their positions \( y \) on the screen. This will give you the distance between the fringes for the two wavelengths.