Assertion (A): The sun appears oval shape at sunrise.
Reason (R): At the time of sunrise sun appears a little before the actual sunrise.
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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Atmospheric refraction causes sunlight to bend as it passes through Earth's atmosphere. This phenomenon makes the sun appear to rise earlier and distorts its shape into an oval or flattened form at the horizon due to differential refraction. Both Assertion (A) and Reason (R) are true, and (R) provides a correct explanation for (A).
Assertion (A): Splitting of light into its component colours is possible in refraction at plane surface of two media.
Reason (R): On each refraction dispersion is possible but in prism at both surface dispersion is in same direction so it is clearly seen.
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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Dispersion, the splitting of light into its constituent colors, occurs during refraction because the refractive index of a medium depends on the wavelength of light. This effect is present at any plane refractive surface. In a prism, the refractions at both surfaces cause deviations for different colors that add up in the same direction, making the overall dispersion more noticeable. Both A and R are true, and R explains A.
Assertion (A): When light passes through a prism, it disperses while if the same light passes through a rectangular glass slab of same material, it doesn’t disperse.
Reason (R): Dispersive power of prism is non zero while that of glass slab is zero.
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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A prism disperses light because its non-parallel surfaces separate colors due to varying refractive indices. A rectangular slab also disperses light internally, but the emergent rays are parallel, resulting in no net angular dispersion. Dispersive power is a material property and is non-zero for any dispersive medium, including glass slabs.
Assertion (A): When white light passes successively through two identical prisms, one inverted with respect to other, then in emergent side, again white light is obtained.
Reason (R): Prism has no ability to create colour but it only separates the colours already present in white light.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
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Assertion (A) is true; the second inverted prism recombines the dispersed light back into white light. Reason (R) is true; prisms only disperse existing colours, they do not create new ones. Reason (R) correctly explains Assertion (A).
Assertion (A): A ray of white light shows no dispersion on emerging from a glass slab although there occurs dispersion inside the glass slab.
Reason (R): The velocity of light inside the glass slab is same for all different colours.
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; due to the parallel surfaces of the glass slab, the dispersed colors recombine upon emerging, showing no net dispersion. Reason (R) is false; dispersion occurs precisely because the velocity of light (and thus refractive index) varies for different colors within the medium. Thus, A is true and R is false.
Assertion (A): A completely transparent material will be invisible in vacuum, when the refractive index is unity.
Reason (R): The ratio of the refractive index of red light to blue light in vacuum is less than unity.
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; if a material's refractive index matches the surrounding (vacuum, \(\mu=1\)), light passes through without deviation or reflection, making it invisible. Reason (R) is false; in vacuum, the refractive index is \(1\) for all colors, so their ratio is \(1\), not less than unity. Thus, A is true and R is false.
Assertion (A): For every observer rainbow is a personal one.
Reason (R): Every observer intercepts light from same water drops.
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; a rainbow's apparent position depends on the observer's location and the specific light rays from water droplets they intercept. Reason (R) is false; different observers see rainbows formed by light from *different* sets of water drops at different angles. Thus, A is true and R is false.
Assertion (A): When white light passes through a prism, deviation of violet light is more than green light.
Reason (R): In a prism average deviation is measured as deviation of yellow light.
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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Violet light has the highest refractive index in a prism, so it deviates most, hence (A) is true. Yellow light is generally used for average deviation calculations in dispersion, so (R) is true. However, (R) does not explain (A).
Assertion (A): A rectangular glass slab produces no deviation and no dispersion.
Reason (R): Dispersive power of glass slab is zero.
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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A rectangular glass slab causes no net angular deviation but does produce lateral shift. It causes dispersion for polychromatic light. So (A) is false. Glass, being a dispersive medium, has a non-zero dispersive power. So (R) is false. Thus, both (A) and (R) are false.
Assertion (A): A prism of refracting angle \(60^{\circ}\) is made of a material of refractive index \(\sqrt{2}\) for a certain wavelength. As light of this wavelength passes through the prism, the prism, angle of minimum deviation is \(30^{\circ}\).
Reason (R): At minimum deviation, angle of refraction of the first face is \(r_1 = A/2 = 30^{\circ}\).
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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For a prism at minimum deviation, the angle of refraction at the first face is \(r_1 = A/2\), where \(A\) is the prism angle. Given \(A = 60^{\circ}\), \(r_1 = 30^{\circ}\). This makes Reason (R) true. Using the prism formula \(n = \frac{sin((A + \delta_m)/2)}{sin(A/2)}\), with \(n=\sqrt{2}\) and \(A=60^{\circ}\), we find \(\delta_m = 30^{\circ}\). Thus, Assertion (A) is also true. Reason (R) provides a key condition used in calculating the minimum deviation, hence it is the correct explanation for (A).