Daniel wants to find out if he can notice the difference in light intensity when he adds some lit candles to a set of 50 lit candles. When he adds 5 candles to the set, he notices the difference in intensity half the time. However, when he adds less than 5 candles to his set, he does not notice any difference in the intensity of light. In this scenario, Daniel's difference threshold for detecting the change in light intensity is lit candles.

5

Explanation:

The light intensity may be defined as the strength of the light or the magnitude of its brightness that a source of light can produce.

The light threshold is the minimum intensity of the light that our eye can detect and the ability to adapt to darkness.

In the context, Daniel wishes to find if can notice the difference in the intensity of the light when he add 5 candles to the set of 50 candles.

He noticed that when he added 5 candles, he could notice the difference in the intensity and when he added less than 5 candles to the set of 50 candles he could not detect.

Thus, the difference threshold for Daniel to detect the change in the intensity of the light is 5 candles.