Answer:
84kg
Explanation:
If the mass of an astronaut in on the moon is 84kg on the moon. After the 3weeks in returning home, his weight will not change. The mass of the astronaut will remain the same which is 84kg. This is so because the acceleration due to gravity experienced by the body remains the same both in the earth and in moon.
Answer: f = -12 cm
Explanation: <u>Combined</u> <u>lenses</u> is an array of simple lenses with a common axis. The combination is useful for correction of optical aberrations which cannot be corrected by simple lenses.
When two lenses are in contact and are thin, focal lengths are related as:

If there is a distance between the lenses, the focal length will be:

Since the lenses in the question above are thin and in contact, the focal length of one of them will be:




-12
The focal length of the other lens is -12 cm, with the negative sign meaning it's a converging lens.
Answer:
The correct option is: d. Fiber-optic
Explanation:
A fiber-optic cables or an optical-fiber cable is a cable that is composed of a bundle of optical fibers. These cables are used for transmitting information or digital signals over long distances.
Each optical fiber in an optical-fiber cable is individually coated with a protective plastic cover and contained in a protective tube. Therefore, an optical-fiber cable is not affected by any electromagnetic interference or radio frequency interference.