[A] : Ultrasound (in sonography ) is the sound beyond the range of human hearing
[R] : Vibrating crystals is the source of ultrasound

Options

A. If both A and R are true and R is the correct explanation of A
B. If both A and R are true but R is not the correct explanation of A
C. If A is true and R is false
D. If both A and R are false

Answer

To solve the question, we need to analyze both the assertion [A] and the reason [R] provided:

### Step-by-Step Solution:

1. **Understanding the Assertion [A]:**
- The assertion states that "Ultrasound in sonography is the sound beyond the range of human hearing."
- **Analysis:** Ultrasound refers to sound waves that have frequencies higher than the upper limit of human hearing, which is typically around 20 kHz. Therefore, this statement is true.

2. **Understanding the Reason [R]:**
- The reason states that "Vibrating crystals is the source of ultrasound."
- **Analysis:** Ultrasound is indeed produced by vibrating crystals, particularly in devices like ultrasound machines where piezoelectric crystals convert electrical energy into mechanical vibrations, generating ultrasound waves. Thus, this statement is also true.

3. **Determining the Relationship Between [A] and [R]:**
- We need to assess whether the reason [R] correctly explains the assertion [A].
- While both statements are true, the reason does not directly explain why ultrasound is beyond the range of human hearing. It merely states how ultrasound is generated.

4. **Conclusion:**
- Since both [A] and [R] are true, but [R] does not serve as the correct explanation for [A], the correct option is:
- **Option B:** Both A and R are true, and R is not the correct explanation of A.

### Final Answer:
The correct option is **B**: Both A and R are true, and R is not the correct explanation of A.

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