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. Sonics / सोनिक
B. Ultrasonics / अल्ट्रासोनिक
C. Supersonics / सुपरसोनिक
D. Imrasonics / इंफ्रासोनिक

Answer

D

Explanation

श्रव्य रेंज की आवृत्ति 20 Hz-- 20,000 Hz होता है। श्रव्य रेंज से कम आवृत्ति को इंफ्रासोनिक तथा श्रव्य रेंज से अधिक आवृत्ति को अल्ट्रासोनिक कहा जाता है।