Topic: Interference and Young's double-slit experiment· Optics

In a double slit experiment, when light of wavelength 400 nm was used, the angular width of the first minima formed on a screen placed 1 m away, was found to be 0.2^°. What will be the angular width of the first minima, if the entire experimental app…

In a double slit experiment, when light of wavelength 400 nm was used, the angular width of the first minima formed on a screen placed 1 m away, was found to be \(0.2^\circ\). What will be the angular width of the first minima, if the entire experimental apparatus is immersed in water ? (\(\mu_{water} = 4/3\))

1. \(0.266^\circ\)

2. \(0.15^\circ\)

3. \(0.05^\circ\)

4. \(0.1^\circ\)

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Answer: 2. \(0.15^\circ\)

For the first minimum, \(\sin\theta=\dfrac{\lambda}{d}\). The angle is small, so \(\theta\propto\lambda\).

In water, \(\lambda'=\dfrac{\lambda}{\mu}=\dfrac{3}{4}\lambda\).

\(\theta'=\tfrac34\times0.2^\circ=0.15^\circ\).

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In a double slit experiment, when light of wavelength 400 nm was used, the angular width of the first minima formed on a screen placed 1 m away, was found to be 0.2^°. What will be the angular width of the first minima, if the entire experimental app…

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