What is the science behind Infrared thermometer ?

Infrared thermometers employ a lens to focus the infrared light emitting from the object onto a detector known as a thermopile. The thermopile is nothing but thermocouples connected in series or parallel. When the infrared radiation falls on the thermopile surface, it gets absorbed and converts into heat.

They can also be used for other things:

Infrared (IR) thermometers enable you to measure temperature quickly, at a distance, and without touching the object you're measuring.

They are so useful, easy, and even fun to use that they have become as common in kitchens as they have on factory floors.

Explanation: :)

Hope this helps.

Infrared thermometers employ a lens to focus the infrared light emitting from the object onto a detector known as a thermopile. The thermopile is nothing but thermocouples connected in series or parallel. When the infrared radiation falls on the thermopile surface, it gets absorbed and converts into heat.

if they have a finite resultant

answer: 2×10^-2kg

explanation: density= mass per volume

vol=mass/density

converting to s.i units we have;

3÷1000kg = 0.003

1.5÷100m = 0.15

0.003/0.15 = 0.02kg