1 nano-meter radiations are very difficult to observe from the ground based telescope because most of this range of radiation is absorbed through ozone layer. A very small amount of this range escape out of the ozone layer. This remaining few radiations are very difficult to track from the ground base telescope.
1 millimeter range of radiation comprises of infrared. It has range from 710 nano-meter to 1 millimeter. Infrared radiation can be easily absorbed from water and carbon di oxide molecules present in the atmosphere. So, it is absorbed by water and carbon di oxide molecules in the atmosphere. Thus, it is difficult to observe from the ground based telescope.
100 meter radiations are are radio-waves. The charged particle present in the uppermost layer of atmosphere absorbs these radio waves. So, these waves are absorbed by charged particle in the upper atmosphere. Thus, it is difficult to observe from the ground based telescope.
focal length f = -30 (negative because it is concave lens)
object distance u = 60
image distance v= unknown
1/-30 = 1/60 + 1/v
v = -20
So, the image is 20cm from lens (on the same side along with the object), and it is virtual (because of negative sign) and erect (concave lens must produce erect images).
An object at rest will remain at rest unless acted on by a force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by a force.
