Question

Human eye cannot see the following range of light spectrum but can be recorded through photography :

• A. 750 nm to 1000 nm
• B. 380 nm to 700 nm
• C. 400 nm to 700 nm
• D. 400 nm to 650 nm

Hint:

Infrared light lies beyond the visible red spectrum and can be captured using special photographic equipment even though humans cannot see it.

Answer 1

The Correct Option is A

Concept: The human eye can normally detect visible light approximately in the wavelength range: \[ 380 \text{ nm} \text{ to } 700 \text{ nm} \] Light beyond this range becomes invisible to human vision. Infrared radiation lies beyond the visible red spectrum and can often be captured using special photographic or digital imaging techniques. The question asks which wavelength range cannot be seen by the human eye but can still be recorded through photography.

Step 1: Understanding the visible light spectrum. Visible light includes:
• Violet light near 380 nm
• Red light near 700 nm Anything beyond this range is invisible to normal human vision.

Step 2: Understanding infrared photography. Infrared radiation exists beyond red light: \[ > 700 \text{ nm} \] Infrared photography uses special sensors or films to capture wavelengths invisible to humans.

Step 3: Analyzing Option (A) 750 nm to 1000 nm. This wavelength range lies in the infrared region. Humans cannot normally see it, but cameras and photographic equipment can record it using infrared technology. Therefore, this option is correct.

Step 4: Analyzing Option (B) 380 nm to 700 nm. This is the visible spectrum itself. Humans can clearly see this range. Hence, Option (B) is incorrect.

Step 5: Analyzing Option (C) 400 nm to 700 nm. This is also part of visible light. Therefore, it is visible to the human eye. Hence, Option (C) is incorrect.

Step 6: Analyzing Option (D) 400 nm to 650 nm. This range is fully visible to humans as well. Hence, Option (D) is incorrect. Final Conclusion: The wavelength range invisible to the human eye but recordable through photography is: \[ \boxed{750 \text{ nm to } 1000 \text{ nm}} \] Therefore, the correct option is: \[ \boxed{(1)} \]