Question

Assertion :Beat frequency between two tuning forks A and B is 4 Hz. Frequency of A is greater than the frequency of B. When A is loaded with wax, beat frequency may increase or decreases. Reason: When a tuning fork is loaded with wax its frequency decreases.

• A. both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. assertion is correct but Reason is incorrect
• D. assertion is incorrect but Reason is correct

Answer 1

The correct option is B both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

Given : Beat frequency $b=f_A-f_B=4$

Let the initial frequency of A be $f_A=256Hz$ and that of B be $f_B=252Hz$

Loading wax on a tuning fork A will decrease its frequency $\left(f_A\right)$.

Let say its frequency becomes either $246Hz$ OR $254Hz$

Now new beat frequency $b^{\prime }=|f_A^{\prime }-f_B|$

Case 1 : $f_A^{\prime }=254Hz{f}_B=252Hz$

$⟹b^{\prime }=|254-252|=2Hz$, means beat frequency is decreased.

Case 1 : $f_A^{\prime }=254Hz{f}_B=252Hz$

$⟹b^{\prime }=|246-252|=6Hz$, means beat frequency is increased.