Answer:
f = 4000 / 30 sec = 133.3 vibrations/sec
P = 1 / f = .0075 sec period of 1 vibration
A diverging lens never produces a real image because the actual light rays never converge. They always diverge. ... A diverging virtual image is always SMALLER than the object. A converging virtual image is always LARGER than the object
DO YOU HAVE THE ENGLISH TRANSLATION?
The Earth's core is estimated to be bigger than both Mars and Mercury. However, I would say that Mercury is the safest choice. Mercury is also known to be smaller than Jupiter's Moon!