Answer:
A) 6.15×10^14 per sec
B)2.5 sec
Step-by-step explanation:
Wavelength of light = 488 nm
speed of light = 3×10^8 m/s
therefore, frequency of light

⇒

⇒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=

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