How much does light increase with each stop change?

When discussing exposure settings in photography, a "stop" refers to a doubling or halving of the amount of light that reaches the camera sensor. When you increase exposure by one stop, you effectively double the amount of light. This means that if you change the exposure setting to allow more light, such as opening up the aperture or slowing down the shutter speed, the light increases by a factor of two.

In contrast, a decrease of one stop results in halving the light that reaches the sensor, which is essentially the reverse effect. The other options in the question do not accurately reflect how stops function in terms of light—either misstating the increase or suggesting no change, which is not consistent with the principles of exposure in photography. Thus, the correct understanding of a "stop" is that it results in an increase of light by a factor of two for each stop change in the positive direction.