Question

Hot iron emits ______ rays which are _______ to the eyes.

• A. infrared, visible
• B. ultraviolet, visible
• C. infrared, invisible
• D. ultraviolet, invisible

Answer 1

The correct option is C

infrared, invisible

Explanation of the correct option-

1. The human eye can see only those lights which fall into the visible spectrum of light. (that is between $380nm-700nm$ wavelength).
2. Infrared radiation comes after the red light in the light spectrum that has a longer wavelength$700nm$. Thus it is invisible to the human eye.

Thus, hot iron emits infrared rays which are invisible to the eye.

Hence, option C is the correct answer.