The area of the bar over r=4 is 0.468
This question involves the concepts of echo, ultrasonic images, ultrasonic sound waves.
The process of ultrasonic images uses the "echo" property of the sound waves.
Echo is the property of the sound wave by the virtue of which the sound wave reflects back to the source of the sound after hitting a surface or an object.
Ultrasonic images are obtained from inside organs of our body. This process involves the use of ultrasonic sound waves that have a frequency greater than 20,000 Hz. These sound waves are out of the range of audible sound by the human ear. When these ultrasonic sound waves are sent in form of pulses into the human body by the use of probes, they reflect back from the tissues of different organs to the probe. The probe then records the reflection properties of these sound waves and displays them in form of an image, known as ultrasonic images.
Learn more about echo here:
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The attached picture shows the process of ultrasonic imaging.
Hello! The nontoxic, nonflammable chemicals containing atoms of carbon, chlorine, and fluorine that have created a hole in the ozone layer are the Chlorofluorocarbons (CFCs)
These are compounds developed and improved by Thomas Midgley in the late 1920s. They were used as refrigerants and aerosol propellants.
These compounds created a hole in the ozone layer by the following reactions:
CCl₃F → CCl₂F· + Cl· (In the presence of light. Radical Reaction)
Cl· + O₃ → ClO + O₂
ClO + O₃ → Cl· + O₂
The last 2 reactions can repeat in a radical mechanism and explain why these compounds are so harmful to the ozone layer.
Answer: Instantaneous speed.
Explanation: