Diffraction MCQ Level -2 - Physics MCQ

In 2-slit interference, the interference fringe spacing y is given by

y = λD/d (e.g. see 1st link).

where D is screen distance and d = slit separation

That's a standard formula, though you may have been taught it using different symbols.

In this question, D = 1.00m and d = 1.00mm = 0.00100m

y = 644x10⁻⁹ x 1.00 / 0.00100

. .= 6.44x10⁻⁴ m

. .= 0.644mm

The bright and dark fringes (B and D)are arranged outwards from each side of the centre like this

BDBDBD

↑

centre

The first dark fringe is therefore y/2 from the centre and the third dark fringe is y/2 + y + y = 2.5y from the centre.

From the centre to the third dark interference fringe is 2.5 x 0.644 = 1.61mm.

The correct answer is: polarization

In Double Slit Fraunhofer Diffraction, there are certain angles where the interference maxima and Diffraction minima overlap. These orders of interference pattern are missing in the pattern. It is known as Absent Spectra.

The correct answer is: 3 : 2

The correct answer is: diffraction

When white light is used instead of monochromatic light, then the central maximum remains white as all seven wavelengths meet there in the same phase. The first minimum and second maximum will be formed by violet color due to its shortest wavelength while the last is due to the red color as it has the longest wavelength. Thus, a colored pattern is observed. However, after the first few colored bands, the clarity of the band is lost, due to overlapping.

The correct answer is: 5.30 x 10³ lines/cm

In Fraunhofer Diffraction, the source of light and the screen are effectively placed at infinite distance. Two convex lenses are used for achieving such a condition. Thus, the incident waveform is plane and the secondary wavelets are in the same phase at every point in the plane of the aperture.