Measuring Intensity of Sources of Light

In summary, to measure the intensities of different sources of light such as candle light and tungsten filament, you will need two things: a device to direct light from the source to a sensor, and the sensor itself which converts light into electricity. It is important to carefully consider the quantities involved, including intensity (measured in W/sr), irradiance (measured in W/m^2 at the observer), and radiant emittance (measured in W/m^2 at the source). In this context, it is recommended to use the term "radiant intensity" to avoid confusion with the traditional definition of "intensity" in physics.
  • #1
shaddy
1
0
how do i measure the intensities of different sources of light?
eg. candle light, tungsten filament etc.
 
Science news on Phys.org
  • #2
You must have at least two things : first, something that can direct light from the source to the cell and secondly the cell (sensor) that can convert light into electricity.
The 1st part can be made very simply as a narrow tube which is long enough so the sensor can only receive light from the source.
 
  • #3
Be careful with your quantities here.

Intensity = W/sr
Irradiance = W/m^2 (at the observer)
Radiant Emittance = W/m^2 (at the source)

Which specifically do you want to measure (I'm guessing Irradiance).

Claude.
 
  • #4
Claude, that's an unusual set of definitions, you should consider calling W/sr "radiant intensity" to distinguish it from the notion of "intensity" that is normally used in at least early undergraduate physics.
 

1. How is the intensity of light measured?

The intensity of light is typically measured in units of Watts (W) or Lumens (lm). This can be done using a specialized instrument called a radiometer, which measures the power of electromagnetic radiation emitted by a source. Alternatively, a photometer can be used to measure the perceived brightness of light, which is directly related to its intensity.

2. What factors affect the intensity of light from a source?

The intensity of light from a source can be affected by factors such as distance from the source, the angle at which the light is measured, and the properties of the medium through which the light travels. Other factors, such as the type of light source and its power, can also play a role in determining the intensity of light emitted.

3. How does the intensity of light change with distance?

The intensity of light follows an inverse square law, meaning that as the distance from the source increases, the intensity decreases exponentially. This is because the same amount of light is spread out over a larger area as it travels further from the source.

4. How is the intensity of light affected by the medium through which it travels?

The intensity of light can be altered by the medium through which it travels. For example, light may be absorbed or scattered by particles in the air, leading to a decrease in intensity. In some cases, such as in a vacuum, light can travel without any loss of intensity.

5. Can the intensity of light be increased?

Yes, the intensity of light can be increased by using reflective surfaces or lenses to concentrate the light in a specific direction, or by increasing the power of the light source. However, the intensity of light cannot be increased indefinitely, as it is limited by the power of the source and the properties of the medium through which it travels.

Similar threads

Replies
16
Views
2K
  • Optics
Replies
10
Views
780
Replies
3
Views
1K
Replies
3
Views
1K
Replies
4
Views
4K
Replies
17
Views
2K
Replies
2
Views
1K
Back
Top