Question

Optical brighteners are common components of soaps and detergents (Assertion A). They help to make fabrics clear, clean and bright on laundering. They alter the reflectance characteristics of the fabric surface and produce a visual effect of whiteness and brightness (Reason R).

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
• B. Both (A) and (R) are correct but (R) is not the correct explanation of (A)
• C. (A) is correct but (R) is not correct
• D. (A) is not correct but (R) is correct

Hint:

Remember that in such questions, it's important to evaluate both statements independently before determining if one correctly explains the other.

Answer 1

The Correct Option is A

Step 1: Concept
Optical brighteners are additives used in detergents to enhance the appearance of fabrics by making them appear whiter and brighter. They work by absorbing ultraviolet (UV) light and re-emitting it as visible blue light, which counteracts the yellowish tinge that fabrics can acquire during washing.

Step 2: Meaning
Assertion A states that optical brighteners are common components in soaps and detergents. Reason R explains how these brighteners alter fabric reflectance to produce a visual effect of whiteness and brightness.

Step 3: Analysis
To analyze the correctness of both assertion (A) and reason (R), we need to consider their individual validity and whether reason (R) correctly explains assertion (A). Assertion A is correct because optical brighteners are indeed commonly used in soaps and detergents. They serve a practical purpose by enhancing the visual appearance of fabrics during washing. Reason R accurately describes how optical brighteners function: they absorb UV light and re-emit it as blue light, which helps to counteract any yellowish tinge on fabric surfaces, thus making them appear whiter and brighter. This explanation is consistent with the mechanism of action of optical brighteners. Given that both assertion (A) and reason (R) are correct, we need to determine if reason (R) correctly explains assertion (A). The statement in R provides a detailed explanation of how optical brighteners work, which directly supports why they make fabrics appear whiter and brighter. Therefore, reason (R) is indeed the correct explanation for assertion (A).

Step 4: Conclusion
Both assertion (A) and reason (R) are correct, with reason (R) providing an accurate explanation of assertion (A). Final Answer: (A)