The speed of light is constant in ALL frames of reference. That is 2.9 x10^8 m/s (290,000,000 m/s). It is independent of the motion of the light source.
Answer:
Wavelength of the x rays is 
Explanation:
It is given that,
The inter planer spacing between the crystal planes, 
The first-order maximum in the Bragg reflection occurs when the incident and reflected x rays make an angle of 39.4 degrees with the crystal planes. According to the Bragg's condition, the first-order maximum is given by :

n = 1



So, the wavelength of the x rays is
. Hence, this is the required solution.
Explanation:
When an object is moving in a circular path, the motion of the object is called uniform circular motion. The object moves under the action of centripetal acceleration. It is given by :

r is the radius of circular path
v is the speed of the object
In uniform circular motion, the object moves with constant speed. Also, the velocity of the object keeps on changing because it changes direction at every instant of time. Also, the object is accelerating due to change in velocity.
So, the correct options are (b) and (c).
The chemical symbol for the element zinc is Zn.
<h3>What is element?</h3>
A chemical element is the one which reacts with other elements to form a compound.
Any chemical symbol must have its first letter written in Uppercase. If the element has two letter chemical symbol, then it should be written in lowercase.
Thus, the student wrote Zn as the chemical symbol of Zinc on the whiteboard.
Learn more about element.
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