Which statement about CCDs is incorrect?

• A. They convert light into X-ray photons
• B. They convert light into electrical charge
• C. They store charge in capacitors
• D. They respond to light by generating electron-hole pairs

Answer: (A)

Light that hits a CCD is converted into electrical charge, not into new photons. When photons are absorbed in silicon, they create electron-hole pairs; the electrons are collected in each pixel’s potential well, which acts like a tiny capacitor. The amount of charge stored in a pixel is proportional to the light intensity it received, and that charge is then shifted out of the array to a readout amplifier to form an image. The statement about converting light into X-ray photons would imply upconversion, which isn’t how CCDs operate. Some CCDs can detect X-rays by generating charge from X-ray photons, but even then the process is converting the incident photons into electrical charge, not producing X-ray photons from light.