Question

An argon ion laser emits light of wavelength of 488 nm. (a) Calculate the frequency of the light. (b) Suppose a pulse of light from this laser is sent from Earth, is reflected from a mirror on the moon, and returns to its starting point. Calculate the time elapsed for the round trip, taking the distance from Earth to the moon to be 3.8×10^5 km.

Answer 1

Answer:

A) 6.15×10^14 per sec

B)2.5 sec

Explanation:

Wavelength of light = 488 nm

speed of light = 3×10^8 m/s

therefore, frequency of light  $\nu=\frac{c}{\lambda}$

⇒ $\nu=\frac{3\times10^8}{488\times10^{-9}}$

⇒ν= 6.15×10^14 per sec

b) distance between moon and earth =  3.8×10^5 km.

= 3.8×10^8 m

light travel from earth moon and back to earth

therefore, distance traveled= 2× 3.8×10^8 m = 7.6×10^8 m

therefore time= distance/speed

⇒ time= $\frac{7.6\times10^8}{3\times10^8}$

= 2.5 sec

So, for a round trip time required is 2.5 sec.