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Regarding Young's double-slit experiment and the dependence on the wavelength of light used, which of the following statements is correct? (A) A larger wavelength gives a larger fringe width. (B) The position of the central maximum depends on the wavelength. (C) With white light, violet forms its first maximum closest to the central maximum. (D) The central maxima of all wavelengths coincide.

1. A larger wavelength gives a larger fringe width.
2. The position of the central maximum depends on the wavelength of light used.
3. With white light, violet forms its first maximum closest to the central maximum.
4. Only statements (A), (C) and (D) are correct; statement (B) is wrong.

Correct answer: Only statements (A), (C) and (D) are correct; statement (B) is wrong.

Solution

Fringe width beta = lambda*D/d increases with wavelength, so (A) is correct. The central maximum is at zero path difference, independent of wavelength, so its position does NOT depend on wavelength: (B) is false, and consequently the central maxima of all wavelengths coincide, making (D) correct. The first-order maximum is at x1 = lambda*D/d, so the shortest visible wavelength (violet) has its first maximum nearest the center, making (C) correct. Therefore A, C and D are correct while B is incorrect.

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