Physics

Physics

Problem

A pair of slits separated by 0.20 mm is illuminated with monochromatic light of wavelength 500 nm. A screen is placed 2.0 m from the slits. According to the small-angle prediction, how far from the central maximum will the second bright fringe appear on the screen? a) 0.10 cm0.10\text{ cm} b) 0.50 cm0.50\text{ cm} c) 1.0 cm1.0\text{ cm} d) 1.25 cm1.25\text{ cm}
Intuitive explanation

This is a double-slit interference problem where you're finding the position of a bright fringe using the small-angle approximation. The key insight is that bright fringes occur when light from both slits travels a path-length difference of exactly mλm\lambda (where mm is an integer), and the small-angle approximation lets you convert that path difference into a simple linear distance on the screen. For the second bright fringe, you need m=2m = 2, then use geometry to relate the path difference to the fringe position.

Intuitive explanation

This is a double-slit interference problem where you're finding the position of a bright fringe using the small-angle approximation. The key insight is that bright fringes occur when light from both slits travels a path-length difference of exactly mλm\lambda (where mm is an integer), and the small-angle approximation lets you convert that path difference into a simple linear distance on the screen. For the second bright fringe, you need m=2m = 2, then use geometry to relate the path difference to the fringe position.

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