Ultrasonic and Infrasonic Waves: The sound having frequency 20 Hz to 20 KHz is called audible sound Human ear cannot hear sound of frequencies lying outside this range. The limits of audibility of sound vary from individual. Generally the upper limit decreases with increase of age of individual, usually and people can not hear sound of frequency more than 15 kHz.
Sound of frequencies below 20 Hz are called infrasonics, while frequencies beyond 20 kHz are called ultrasonics. Ultrasonics can be heard by dogs, cat bats etc. Bats detect the path by means of ultrasonics. Ultrasonics can be used for diagnosis of tumour and other abnormalities within our body. This is known as ultrasonography. Ultrasonics are used to curve various diseases and to measure depth of oceans to detect submarines.
The waves produced by simple pendulum (having time period 2 seconds) are

Options

A. infrasonics
B. audible
C. ultrasonics
D. none of these

Answer

To solve the question regarding the waves produced by a simple pendulum with a time period of 2 seconds, we will follow these steps:

### Step-by-Step Solution:

1. **Understand the Relationship Between Time Period and Frequency:**
The frequency (f) of a wave is inversely related to its time period (T). This relationship can be expressed using the formula:
\[ f = \frac{1}{T} \]

2. **Identify the Given Time Period:**
From the question, we are given that the time period (T) of the simple pendulum is 2 seconds.

3. **Calculate the Frequency:**
Using the formula from Step 1, we can substitute the given time period:
\[ f = \frac{1}{T} = \frac{1}{2 \text{ seconds}} = 0.5 \text{ Hz} \]

4. **Classify the Type of Wave Based on Frequency:**
Now that we have calculated the frequency, we need to classify it:
- Frequencies below 20 Hz are classified as infrasonic.
- Frequencies between 20 Hz and 20 kHz are classified as audible.
- Frequencies above 20 kHz are classified as ultrasonic.

Since 0.5 Hz is below 20 Hz, we classify this frequency as infrasonic.

5. **Conclusion:**
Therefore, the wave produced by a simple pendulum with a time period of 2 seconds is classified as an infrasonic wave.

### Final Answer:
The wave produced by a simple pendulum having a time period of 2 seconds is an infrasonic wave.

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