Assertion (A): The best contrast of the interference pattern is obtained when the intensity of the emerging lights from the two slits of the Young’s experimental set-up are equal.
Reason (R): Intensity is proportional to the square of the amplitude.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
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Assertion (A) is true, as equal intensities (\(I_1 = I_2\)) ensure \(I_{text{min}} = 0\) for maximum contrast.
Reason (R) is true, as intensity \(I propto A^2\). However, (R) does not explain why \(I_1 = I_2\) leads to best contrast.
Assertion (A): The central fringe is bright or dark, it dependents on the initial phase difference between the two coherent sources.
Reason (R): The pattern and position of fringes always remains same even after the introduction of transparent medium in a path of one of the slit.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Assertion (A) is true. The nature of the central fringe depends on the initial phase difference. Reason (R) is false. Introducing a transparent medium causes a path difference \((n-1)t\) and shifts the entire fringe pattern.
Assertion (A): Diffraction is a sure indication of wave nature.
Reason (R): Only transverse waves can be diffracted.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Assertion (A) is true; diffraction is a characteristic property of all waves. Reason (R) is false; both transverse (e.g., light) and longitudinal (e.g., sound) waves can be diffracted.
Assertion (A): Sound waves in air cannot be polarised.
Reason (R): Polarisation is the characteristic of light wave only.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Assertion (A) is true; sound waves in air are longitudinal waves and cannot be polarized. Reason (R) is false; polarization is a property of all transverse waves, not exclusively light waves.
Assertion (A): Two polaroids are crossed to each other. When either of them is rotated through \(30^\circ\), then only one eighth of the incident unpolarised light passes through the combination.
Reason (R): According to Malus’s law, \(I \propto cos^2 \theta\) where \(I\) is the resultant intensity transmitted and \(\theta\) is the angle between the optical axis of analyser and polariser.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Assertion (A) is true. Unpolarised light becomes \(I_0/2\) after the first polaroid. With \(60^\circ\) angle between axes, Malus's law gives \(I = (I_0/2)cos^2(60^\circ) = (I_0/2)(1/4) = I_0/8\). Reason (R) correctly states Malus's law, which explains (A).
Assertion (A): At the first glance the top surface of a Morpho’s butterfly’s wing appears a beautiful blue-green. If the wing moves, the colour changes.
Reason (R): Different pigments in the wing reflect light at different angles.
[Hint: It is due to interference of light rays reflected from different layers of wing.]
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Assertion (A) is true. Morpho butterflies exhibit iridescence due to structural coloration. Reason (R) is false. The color is due to light interference by nanostructures on the wings, not pigments.
Assertion (A): The best contrast of the interference pattern is obtained when the intensity of the emerging lights from the two slits of the Young’s experimental set-up are equal.
Reason (R): Intensity is proportional to the square of the amplitude.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
For best contrast in an interference pattern, the amplitudes of the interfering waves must be equal, implying equal intensities. Intensity \(I\) is proportional to the square of the amplitude \(A\), i.e., \(I \propto A^2\). Thus, equal intensities lead to maximum contrast.
Assertion (A): The central fringe is bright or dark, it depends on the initial phase difference between the two coherent sources.
Reason (R): The pattern and position of fringes always remains same even after the introduction of transparent medium in a path of one of the slit.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
The central fringe's nature (bright/dark) depends on the initial phase difference. Introducing a transparent medium with refractive index \(n\) and thickness \(t\) in one path creates an additional path difference \((n-1)t\), shifting the entire fringe pattern. So, (R) is false.
Assertion (A): Diffraction is a sure indication of wave nature.
Reason (R): Only transverse waves can be diffracted.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Diffraction, the bending of waves around obstacles, is a hallmark of wave phenomena, so (A) is true. However, both transverse waves (like light) and longitudinal waves (like sound) can be diffracted, making (R) false.
Assertion (A): We cannot get diffraction pattern from a wide slit illuminated by monochromatic light.
Reason (R): In diffraction pattern, all the bright bands are not of the same intensity.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
A diffraction pattern always exists, but for a very wide slit compared to wavelength, it's very narrow and practically unobservable, making (A) practically true. In single-slit diffraction, the central maximum is brightest, and other maxima are less intense, so (R) is true. (R) does not explain (A).