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brightness

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Secondary Information

Definition

Brightness is a measure of the intensity of light. It is a physical quantity, meaning that it can be measured objectively.

The brightness of a light source is determined by the amount of energy it emits per unit time and the wavelength of the light.

Brightness can be measured in a number of ways, but the most common unit is watts per steradian. One watt per steradian is equal to the amount of light emitted by a one-watt source in a one-steradian beam.

How can the word be used?

The room brightened up when the sun came out.

brightness

Different forms of the word

Noun:

brightness (the quality of being bright).

brightness (the amount of light that is emitted by a source).

Adjective:

bright (having a lot of light).

bright (clear and shining).

Verb:

to brighten (to make something brighter).

to brighten (to become brighter).

Etymology

The word "brightness" comes from the Old English word beorht, which means "bright, shining, or clear." The Old English word beorht is thought to be related to the Proto-Germanic word berhtaz, which also means "bright, shining, or clear.".

Question

What determines the brightness of a bulb?

AQA Science Exam Question and Answer

Question:

Explain the term "brightness" in the context of light. How does the brightness of an object relate to its luminous intensity and distance from an observer?

Answer:

In the context of light, "brightness" refers to the perceived intensity or luminance of an object or light source.

Relationship between Brightness, Luminous Intensity, and Distance:

The brightness of an object depends on its luminous intensity (total power emitted in all directions) and its distance from an observer.

Luminous Intensity: Objects with higher luminous intensity emit more light and appear brighter to an observer. For example, a light bulb with higher wattage will have higher luminous intensity and appear brighter than a bulb with lower wattage.

Distance: The brightness of an object decreases with an increase in distance from the observer. This relationship follows the inverse square law, meaning the brightness diminishes rapidly as the distance between the object and the observer increases.

In summary, the brightness of an object is influenced by its luminous intensity and its distance from an observer. Objects with higher luminous intensity will appear brighter, while objects farther away from the observer will appear dimmer due to the inverse square law.