A.) Hertz is the measuring unit for frequency!!
[Your explanation is correct]
Hope this helps!
Answer:
They contain iron.
Explanation:
Iron is made of metal and magnets attract to metal Iron.
Thick lens will have shorter and consequently thin lens will have greater focal length. Because, For a thick lens, the optical path length of the light is more, than for a thin lens, thus, the bending of light will be more in case of a thicker lens. Consequently, it has a shorter focal length.
My calculations state, not rounding, the mass is 1.8
