An observer uses a periscope to look over a tall barrier. The periscope contains two flat parallel mirrors, as shown in the diagram.
a.[3]
Complete the ray diagram to show how a ray of light passes through the periscope from the object to the observer's eye. You must:
- Draw the path of the light ray after reflecting from Mirror 1 to Mirror 2, and then to the observer's eye.
- Draw the normal line at the point of incidence on Mirror 2.
b.[2]
The observer uses the periscope to watch waves on a lake.
The observer counts 24 complete wave crests passing a fixed marker in 2 minutes. Calculate the time period of one wave in seconds.
c.[2]
A different wave has a frequency of 0.4 Hz0.4\text{ Hz}0.4 Hz and a wavelength of 30 m30\text{ m}30 m. Calculate the speed of this wave.