An object vibrated with a frequency of 15 Hz. Which of the following is true ?

Options

A. It produces sound which we can hear.
B. It does not produce sound.
C. t produces sound which we cannot hear.
D. It produces sound which we can hear if we strain our ears.

Explanation

To determine which statement is true regarding an object vibrating with a frequency of 15 Hz, we can follow these steps:

### Step 1: Understand the concept of frequency
Frequency is the number of vibrations or cycles that occur in one second. It is measured in Hertz (Hz).

### Step 2: Identify the range of human hearing
The human ear can typically hear sounds in the frequency range of 20 Hz to 20,000 Hz. Sounds below 20 Hz are considered infrasound, while sounds above 20,000 Hz are considered ultrasound.

### Step 3: Compare the object's frequency to the audible range
The object in question vibrates at a frequency of 15 Hz. Since 15 Hz is below the minimum threshold of human hearing (20 Hz), it falls into the category of infrasound.

### Step 4: Analyze the options provided
1. It produces sound which we can hear.
2. It produces sound which we can't hear.
3. It does not produce sound.
4. It produces sound which we can hear if we extend our ears.

Given that 15 Hz is below the audible range, we can conclude that the sound produced by the object is not audible to humans.

### Step 5: Select the correct option
Based on the analysis, the correct option is:
- Option 2: It produces sound which we can't hear.

### Final Answer
The correct answer is: **It produces sound which we can't hear.**

---