Exams › JEE Advanced › Physics

In a setup like Young's double-slit experiment, slits S1 and S2 are fed by coherent microwave sources of frequency 10⁶ Hz, synchronized to zero phase difference, and separated by d = 150.0 m. The intensity I(theta) is recorded versus theta at a large distance, with I0 the maximum intensity. For 0 <= theta <= 90 deg, which statement about I(theta) is correct?

1. I(theta) = I0/2 at theta = 30 deg
2. I(theta) = I0/4 at theta = 90 deg
3. I(theta) = I0 at theta = 0 deg
4. I(theta) is constant for all theta.

Correct answer: I(theta) = I0 at theta = 0 deg

Solution

Here lambda = c/f = (3*10⁸)/(10⁶) = 300 m and d = 150 m = lambda/2. At theta = 0 the path difference is zero, so the waves arrive in phase and I = I0 (central maximum). This makes option C correct. (At theta = 90 deg, path diff = d = lambda/2 -> minimum, so I = 0, not I0/4.)

Related JEE Advanced Physics questions

• What factor influences the visibility of fringes in an interference pattern?
• When the screen is moved further along the x-axis away from the source, which of the following statements is false?
• In the Young's double slit experiment using a monochromatic light of wavelength λ, the path difference (in terms of an integer n) corresponding to any point having half the peak intensity is
• Using the expression 2d sin θ = λ, one calculates the values of d by measuring the corresponding angles θ in the range 0 to 90°. The wavelength λ is exactly known and the error in θ is constant for all values of θ. As θ increases from 0°:
• Two coherent point sources separated by a distance d = 5 micrometers emit light of wavelength lambda = 2 micrometers in phase. A circular wire of radius R = 20 micrometers is placed symmetrically around the two sources (sources lie along a diameter). Points A and B are at the ends of the diameter along the line joining the sources; points C and D are at the ends of the diameter perpendicular to the line joining the sources. Which of the following is correct?
• Young's double slit experiment is performed in a medium of refractive index mu1 = 4/3. A thin transparent slab of refractive index mu2 = 3/2 and thickness t = 8 micrometers is placed in front of slit S2. The magnitude of the optical path difference (with respect to the liquid medium) at the central point O is:

⚔️ Practice JEE Advanced Physics free + battle 1v1 →