Exams › JEE Main › Physics

In a Young's double-slit experiment using monochromatic light, how can the central bright fringe (zero-order maximum) be distinguished from the other bright fringes?

1. It has greater intensity than the other bright fringes.
2. It is wider than the other bright fringes.
3. It is narrower than the other bright fringes.
4. By using white light instead of monochromatic light, the central fringe appears white while others are coloured.

Correct answer: By using white light instead of monochromatic light, the central fringe appears white while others are coloured.

Solution

With single-wavelength light, every bright fringe has the same width and (ideally) the same intensity, so the central fringe cannot be picked out. If white light is used, only the central fringe (zero path difference) has all wavelengths coinciding and therefore appears white, while the surrounding fringes become coloured. Hence using white light identifies the central fringe.

Related JEE Main Physics questions

• The pupil opening of a human eye is about 2 mm. If the average wavelength of visible light is taken as 5000 Å, the eye’s approximate angular resolving limit is
• For a single-slit diffraction pattern, the condition corresponding to the appearance of secondary maxima is
• In a Fresnel biprism setup, the two lens positions give slit separations of 16 cm and 9 cm. What is the true separation between the slits?
• In a Young’s double-slit setup, two monochromatic sources emit light of wavelengths 2500 Å and 3500 Å. Which pair of fringe orders from the two patterns will fall at the same position?
• In a Young’s double-slit setup, the intensity at a bright fringe maximum is I0. The slit separation is d = 5bb, where bb is the wavelength of the light used. If the screen is placed at a distance D = 10d, what intensity is observed at the point directly opposite one of the slits?
• What is the relationship between the polarizing angle and the critical angle?

⚔️ Practice JEE Main Physics free + battle 1v1 →