How to identify whether a new thermos insulated!
People under the irradiation of the sunlight, will feel hot, this is because the heat radiation of the sun to us, this is called thermal radiation. The best way to prevent thermal radiation is put it back, reflective heat mirror is the best material.
This is a way to detect the water inside have broken, the voice is the echo of air flow, the greater the echo, the better!
The empty bottle attached to the ear, echo the bigger the better!
