Which of the following will reduce the frequency of oscillation of a simple pendulum?

Analyze the question: We want to know what change will reduce the frequency of a simple pendulum.

Concept: For a simple pendulum swinging with small amplitude, the period is

T = 2π√(L/g)

and the frequency is the reciprocal:

f = 1/T = (1/2π)√(g/L)

So frequency depends only on:

• L, the length of the string
• g, the acceleration due to gravity

It does not depend on the mass of the bob, and for small angles it does not depend on the amplitude.

Check each option:

• A. Decreasing the length: L gets smaller, so f = (1/2π)√(g/L) increases. ✗
• B. Increasing the amplitude: For small oscillations, there is no effect on f. ✗
• C. Increasing the length: L gets larger, so √(g/L) gets smaller and f decreases. ✓
• D. Increasing the mass of the bob: Mass cancels out, so there is no effect. ✗
• E. Reducing the mass of the bob: Again, no effect. ✗

Answer: Option C, increasing the length of the string.

Tip: Remember "f is inversely proportional to √L". A longer pendulum swings more slowly, like a big grandfather clock, while a short one swings quickly. Mass never matters for a simple pendulum, so in the exam you can eliminate any option about mass immediately.