Think about a thermos bottle. It consists of an inner bottle with a shiny silver surface separated from an outer container by a space with no air. In what ways does it block conduction, convection, and radiation?

Radiation

Explanation:

Conduction, convection and radiation are the three modes of heat transfer.

1. Conduction: When the one end is heated of any rod, the heat transfer to the other end by the vibrational motion of the molecules, it is called conduction.

The heat transfer in a solid is due to the conduction.

2. Convection: When the liquid or gas is heated, the molecules which is in contact to the heat, heated first and due to the decrease in density they moves up and the molecules on the upper side are higher in density so they moves down. These are called convection currents. The process continues till the entire liquid becomes heated. It generally takes place in liquids and gases.  

3. Radiation: The process of heat transfer in which no molecules takes place is called radiation. The heat coming from sun is due to the radiation. It does not require any medium.  

In the thermos bottle, as there is no air between the two layers, so the heat transfer is due to the radiation.  

force required to detach it is given by

charges are taken to be fundamental charge

now we have

so above is the minimum distance at which it will detach