Photoelectric Effect in Photography

The photoelectric effect is a property found in some metals that makes it possible for them to produce electrons when light is directed on their surfaces. When light illuminates on these types of metal, it produces electrons from the surface. The flow of these electrons constitutes an electric current. This is because light has electromagnetic waves, which carry some energy, and when it is shined on a metal, this energy can be transferred. When the energized photons strike particular atoms, the energy is absorbed by the atoms. Sufficient energy is required for the electrons to become free electrons. If the energy is not sufficient, the light is simply reflected.

Photon Energy

The photoelectric effect is used in digital cameras and determines which photon energy will be absorbed. The energy affects frequency and color visible to the human eye. A limited photo surface emits energy which is directly proportional to the color intensity of the light it measures. Digital cameras use this effect to capture images.

Silicon Sensor

Digital cameras capture light and focus it on a silicon sensor using a lens. The sensor is made up of small photosites, or picture elements that are light sensitive. These photosites are referred to as pixels. A digital camera has several million pixels. Some digital cameras function using a charge couple device.

Capacitors

This light sensor has several capacitors where images are projected when you take a picture. When light hits individual capacitors, electrons can be bumped out of atoms, and this charges the capacitor. This is referred to as the photoelectric effect. The amount of charge in a capacitor is determined by intensity of the light directed on it. Once you close the camera shutter, the charge which has collected in all the capacitors is measured to acquire image data.

Image Data

The image data that is collected is used to determine the light intensity in individual pixels. This information can be used to produce black and white images only. The light has to be split into different beams using a digital camera device referred to as beam splitter. The beam splitter will separate the light into green, blue and red beams. Each beam is sent to a different charge couple device. Once all the image data is read, a computer chip is used to determine the real color and concentration of every pixel.

References

• "The Washington Post" Newspaper; Digital Cameras Use Megapixels and Semi-conductors to Capture Everyday Images; Curt Suplee; December 15, 2009
• Cornell Center for Materials Research: Photoelectric Effect is the Reason Digital Cameras Work
• Kavli Institute for Cosmological Physics at the University of Chicago; The Photoelectric Effect and Its Applications; Robert B. Friedman et al.