I believe the answer is the fourth one, hope this helps
Answer:
A basic quantity is basically the physical quantity that can not be defined in terms of other quantities.
Explanation:
A basic quantity is basically the physical quantity that can not be defined in terms of other quantities.
Some of the names of the basic quantities include:
- Mass, denoted by the symbol 'm', with S.I. unit 'kg'
- Length, denoted by symbol 'l', with S.I. unit 'm'
- Time, denoted by symbol 't', with S.I. unit 's'
- Current, denoted by 'I', with S.I. unit 's' 'A'
- Temperature, denoted by 'T', with S.I. unit 'K'
- Amount of substance, denoted by 'n', with S.I. unit 'mol'
- Luminous Intensity, denoted by 'Iv', with S.I. unit 'cd'
- A basic quantity is chosen arbitrarily.
Gamma rays
each section of the electromagnetic spectrum has characteristics energy level, wavelength and frequencies association with it's photons
Answer:
At supersonic speeds (those greater than the local sound speed), there is no sound heard as an object approaches an observer because the object is traveling faster than the sound it produces. Only after the object has passed will the observer be able to hear the sound waves emitted from the object.
Explanation:
