Infra sounds are sounds with frequencies below 20 Hz.The popular concept that infra sounds are in audible holds false
Explanation:
- Some example of Infrasounds are- some animals such as whales, elephants and giraffes which communicate with each other using infrasound over long distances.
- Various natural phenomenon such as Avalanches, volcanoes, earthquakes, ocean waves, water falls and meteors also generate infrasonic waves
- Infrasound, is sound that is lower in frequency than 20 Hz or cycles per second.
- Even the human body can generate mechanical vibrations at very low frequencies, which are known as the infrasonic waves. Such low-frequency vibrations/infrasonic waves are produced by physiological processes—such as heartbeats, respiratory movements, blood flow in vessels, and other processes.
B. Decreases
Why: Because the longer the wavelength the lower the frquency. The shorter the wavelength the higher the frequency.
Answer:
Explanation:
Given
length of string 
frequency 
time taken by wave to reach at other end 
speed of wave is given by
wavelength of is given by
Sunlight emits more energy than artificial light. Sunlight is better and healthier than most artificial lights and helps plants to grow more.
Answer:
absorbs heat and its kinetic energy increases.
Explanation:
As we know that heat is defined as the change in the temperature as there is increase in the temperature change then the heat will increase or decrease with respect to increase or decrease in temperature change.
In the given, question temperature is changing from 20° to 50° which means there is increase in the temperature which results in the absorption of heat. And increase temperature will increase the average speed of the molecules which results in increase in kinetic energy.
