The correct option is (c).
Explanation
Ultrasound refers to high-frequency sound waves (typically above 20 kHz) that can penetrate human tissues. In medical diagnostics, these waves are utilized to visualize internal body structures based on the principle of reflection.
Statement-wise Analysis
- Statement 1 is Correct: Echocardiography is a medical test that uses ultrasound waves to create live images of the heart. It allows physicians to monitor how the heart and its valves are functioning.
- Statement 2 is Incorrect: Ultrasonography is a diagnostic imaging technique used to visualize internal organs such as the liver, gall bladder, kidneys, and uterus. It is not used to correct vision defects. Vision defects (such as myopia or hypermetropia) are corrected using optical lenses or laser surgeries (e.g., LASIK).
- Statement 3 is Correct: The technique of ultrasound imaging relies on the reflection of sound waves. As the waves travel through the body, they reflect off boundaries where there is a change in tissue density. These reflected waves (echoes) are detected and converted into electrical signals to generate an image.
Key Takeaway: Ultrasound is a diagnostic tool that utilizes the reflection of high-frequency sound waves from tissue boundaries; it is distinct from optical treatments used for vision correction.