Does the infrared camera use the linear propagation of light or the refraction of light to measure temperature?

A, rainbows are formed by the refraction of light after rain and cannot be explained by the straight-line propagation of light;

B, the reflection in the water is imaged by a plane mirror, which is formed by the reflection of light and cannot be explained by the straight-line propagation of light;

C, the immediate effect is that the light propagating in a straight line is blocked by an opaque pole, and a shadow is formed in a dark area behind the pole,

which can be explained by the straight line propagation of light;

D, infrared photography is the use of infrared light emitted by objects, through the lens imaging, can not be explained by the linear propagation of light.

Therefore, C.