Night vision glasses detect energy given off by objects as

It detects the Infrared waves and use it to form image

Explanation:

As we know that all objects which are at temperature greater than zero kelvin.

So here when we use night vision glasses then in this case glass has property to detect the infrared waves radiated by the objects which are at room temperature.

So these night vision lens are  sensitive to infrared waves and they used that part of the spectrum to form the image of an object.

Since at room temperature the spectrum given by the objects are lying in the range of visible range so here we can say that it is not visible at that lower temperature by their own.

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