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A thin film of soap solution (n =1.4) lies on the top of a glass plate (n = 1.5). When visible light is incident almost normal to the plate, two adjacent reflection maxima are observed at two wavelengths 400 and 630 nm. The minimum thickness of the soap solution is

(a) 420 nm(b) 500 nm(c) 450 nm(d) 490 nmSolution: Answer: (c)For reflection at the air-soap solution interface, the phase difference is π.For... View Article

Two beams of light will not give rise to an interference pattern, if

(a) They are coherent(b) They have the same wavelength(c) They are linearly polarized perpendicular to each other(d) They are not... View Article

Two coherent sources of different intensities send waves which interfere. The ratio of maximum intensity to the minimum intensity is 25. The intensities of the sources are in the ratio

(a) 25:1(b) 5:1(c) 9:4(d) 625:1Solution: Answer: (c) 9:4 Imax/Imin = 25/1 (given)Therefore, [√I1 + √I2]/[√I1 - √I2] = 5/1using componendo and... View Article

100π phase difference = … path difference.

(a) 10 λ(b) 25 λ(c) 50 λ(d) 100λSolution: Answer: (c) 50 λPath difference = λ/2π x Phase difference= λ/2π x 100 π= 50 λ... View Article

What is the minimum thickness of a thin film required for constructive interference in the reflected light from it? Given, the refractive index of the film = 1.5, wavelength of the light incident on the film = 600 nm.

(a) 100 nm(b) 300 nm(c) 50 nm(d) 200 nmSolution: Answer: (a) Condition for constructive interference is2μt = (2n + 1)λ/2where n = 0,1,2,3,...For... View Article

In a Young’s double slit experiment, the fringe width is found to be 2 mm, when light of wavelength 6000 A is used. Find the change in fringe width if the whole apparatus is immersed in water of refractive index 1.33.

(a) 0.5mm(b) 1mm(c) 1.5mm(d) 2mmSolution: Answer: (c) 1.5mmFringe width, β = Dλ/dWhen immersed in water, the wavelength becomes, λ1 = λ/μNew... View Article

If Young’s double-slit experiment is performed under water, how would the observed interference pattern be affected ?

Solution: Underwater, the wavelength of the light would decrease, λUW = λair/nwater. Since the position of light and dark bands are proportional... View Article

If Young’s double slit experiment is performed in water instead of air, then

(a) No fringes would be seen(b) Fringe width would decrease(c) Fringe width would increase(d) Fringe width would remain unchangedSolution:... View Article

For sustained interference fringes in double slit experiment, essential conditions

Question: For sustained interference fringes in double slit experiment, essential conditions is/are1. sources must be coherent2. the intensities... View Article

In a double slit interference experiment, the fringe width obtained with a light of wavelength 5900 A was 1.2 mm for

Question: In a double slit interference experiment, the fringe width obtained with a light of wavelength 5900 A was 1.2 mm for parallel narrow... View Article

A is an essential condition for coherent sources. Here, A refers to

(a) constant phase difference(b) equal amplitude(c) Both (a) and (b) are correct(d) Both (a) and (b) are incorrectSolution:Answer: (a)Coherent... View Article

Select the right option in the following

(a) Maxwell provides compelling theoretical evidence that light is a transverse wave. (b) Thomas Young experimentally proved the wave behavior... View Article

Why photoelectric effect cannot be explained on the basis of the wave nature of light?

Solution: The wave nature of radiation can not explain the following:(1) The instantaneous ejection of photoelectrons(2) The fact that KE of the... View Article

Which of the following does not support the wave nature of light?

(a) Interference(b) Diffraction(c) Photoelectric effect(d) PolarisationSolution: Answer: (c) Photoelectric effectPhotoelectric effect can be... View Article

The wave theory of light, in its original form, was first proposed by

(a) Isaac Newton(b) Christian Huygens(c) Thomas Young(d) Augustin Jean FresnelSolution:Answer: (b) Christian Huygens... View Article

Which of the following generates a plane wavefront

(a) alpha rays(b) beta rays(c) gamma rays(d) none of theseSolution:Answer: (d)In the given options none of the sources generates a plane... View Article

In Young’s double slit experiment if the slits widths are in the ratio 1 : 9, the ratio of the intensities at minima to that at maxima will be

(a) 1(b) 1/9(c) 1/4(d) 1/3Solution:Answer: (c) 1/4Intensity of fringe is directly proportion to width os the slits. Therefore, I2/I1 = W2/W1 =... View Article

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