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
View Answer
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): Secondary rainbow is fainter than primary rainbow.
Reason (R): Secondary rainbow is seen due to the scattering of primary rainbow through water molecules.
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
View Answer
Assertion (A) is true; secondary rainbows are fainter due to two internal reflections causing more light loss. Reason (R) is false; secondary rainbows result from light undergoing two internal reflections in raindrops, not scattering of a primary rainbow.
Assertion (A): In clear weather, sky appears to be blue not violet.
Reason (R): In clear atmosphere, light of shorter wavelength is scattered more as compared to light of longer wavelength.
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
View Answer
Assertion (A) is true; violet light scatters most, but our eyes are more sensitive to blue. Reason (R) is true; Rayleigh scattering is inversely proportional to the fourth power of wavelength, scattering shorter wavelengths more effectively. Reason (R) correctly explains Assertion (A).
Assertion (A): During sunset and sunrise sun appears to be red.
Reason (R): During sunrise or sunset, sun emits electromagnetic radiations of comparatively higher wavelength only.
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
View Answer
Assertion (A) is true; at sunrise/sunset, sunlight travels longer through the atmosphere, scattering away shorter wavelengths (blue) and leaving longer wavelengths (red). Reason (R) is false; the sun emits all wavelengths. The perceived color is due to atmospheric scattering, not selective emission.
Assertion (A): Iris of the eye contains rods and cones which transmits electric signal to brain through optic nerve.
Reason (R): Rods sense colour of object and cone sense intensity of 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
View Answer
Both Assertion (A) and Reason (R) are false. Rods and cones are located in the retina, not the iris. Rods detect light intensity (dim light), and cones detect color (bright light).
Assertion (A): In total internal reflection reflected light is in the phase with incident light.
Reason (R): Reflecting surface is rarer in TIR.
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
View Answer
In Total Internal Reflection (TIR), light reflects from a denser medium into the same denser medium at the interface with a rarer medium. Reflection at a denser interface causes a \(\pi\) phase change, but in TIR, reflection from an 'optically denser medium-optically rarer medium' boundary results in no phase change in the reflected wave. Thus, (A) is true.
The reflecting surface in TIR is the interface between the denser and rarer media, not 'rarer'. Thus, (R) is false.
Therefore, (A) is true but (R) is false.
Assertion (A): For a Concave mirror, if object is made to accelerate uniformly toward the mirror from infinity, then its image will also show uniform acceleration in opposite direction.
Reason (R): Concave mirror may act as a diverging mirror.
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
View Answer
For a concave mirror, the image acceleration is not uniform, as magnification \(m = -v/u\) changes non-linearly with object position (u).
Thus, (A) is false.
A concave mirror is a converging mirror. It acts as a diverging mirror only when the object is placed between the pole and focus, forming a virtual, erect, and magnified image. However, in general context, it's not a diverging mirror. Thus, (R) is also false.
Therefore, both (A) and (R) are false.
Assertion (A): When two thin equiconvex lens are placed in contact, the effective power of combination may decrease.
Reason (R): Power of lens is defined as ability of bending of 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
View Answer
For two thin lenses in contact, the equivalent power is \(P = P_1 + P_2\). For equiconvex lenses, both \(P_1\) and \(P_2\) are positive. Therefore, the effective power (P) will always increase, not decrease. Thus, (A) is false.
Power of a lens is indeed a measure of its ability to bend or converge/diverge light rays. Thus, (R) is true.
Therefore, (A) is false but (R) is true.
Assertion (A): Although the surface of goggles lens are curved, it does not have any power.
Reason (R): In case of goggles, both the curved surfaces have equal radius of curvature and have centre of curvature on the same side
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
View Answer
Protective goggle lenses do not alter vision, implying their optical power is zero. Thus, (A) is true.
The power of a lens is given by \(P = (n-1)(\frac{1}{R_1} - \frac{1}{R_2})\). If the surfaces have equal radii of curvature and their centers are on the same side (as in a meniscus lens where both surfaces curve in the same direction), then \(\frac{1}{R_1} - \frac{1}{R_2} = 0\), resulting in (P = 0). This explains why curved goggle lenses can have no power. Thus, (R) is true and is the correct explanation of (A).
Assertion (A): Lens formula can be applied only for thin lenses.
Reason (R): For thick lenses one cannot find image position.
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
View Answer
The simple lens formula \(\frac{1}{f} = \frac{1}{v} - \frac{1}{u}\) is an approximation valid for thin lenses. Thus, (A) is true.
For thick lenses, more complex formulae or ray tracing methods are used, but the image position can certainly be found. Thus, (R) is false.
Therefore, (A) is true but (R) is false.