Physics of Light Lessons and Activities for High School Students 13. This leads to a decrease in reflectivity, which depends on the metal's characteristics. Light Intensity In the Science with a Smartphone: Lux Meter activity, students use a cell phone's light sensor and a sensor-based mobile app to measure the brightness (or intensity) of light from different light sources and locations. While many modern cameras have light metering built-in it’s still advantageous to know light levels around the subject, especially for studio or portrait photography. Low light forces a photographer to increase exposure time or open up the lens aperture, and sometimes both. However, in higher frequencies, deviations of Drude`s approach start to appear, because bound electrons of the metal start to respond to the incidence of light, instead of just valence band electrons response. Light intensity is at the heart of photography. It was observed that, at higher wavelengths (lower frequencies), the optical constants of metals are similar to the values of Drude`s function, where the complex refractive index is much smaller then the damping constant, or extinction coefficient. Answer (1 of 9): Intensity of Light is an expression of the amount of light power emanating from a point source within a solid angle of one steredian. This conclusion was derived by Drude and confirmed experimentally by Hagens-Ruben. Luminance is the intensity of light from a surface per unit area in a given direction.
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