Answer:
The observer detects light of wavelength is 115 nm.
(b) is correct option
Explanation:
Given that,
Wavelength of source = 500 nm
Velocity = 0.90 c
We need to calculate the wavelength of observer
Using Doppler effect
Where, 
Hence, The observer detects light of wavelength is 115 nm.
Answer:
1.Stronger bones 2.Joint flexibility
Answer is B.
Because velocity is vector quantity, so magnitud and direction are needed to define it.
Since velocity means the speed(magnitude) of some object in a given direction, so it’s units are usually measured by meters/ seconds
The answer is either c or b
Answer:
the definition of civics is the study of the rights and duties of citizenship.
so the answer is B.
hope this helps.
