Answer: 8W.
Answer analysis: This question mainly examines the calculation of the light output power of LED lamps, and it is necessary to understand the relationship between power, luminous efficiency and light output power.
First, let's clarify the conditions given in the question:
The power of the LED lamp is P = 10W, which means that the LED lamp consumes 10 joules of electricity per second when it is working.
The luminous efficiency of the LED lamp is η = 80%, which means that the efficiency of the LED lamp in converting electrical energy into light energy is 80%. In other words, only 80% of the electrical energy is converted into light energy, and the remaining 20% may be converted into heat energy or other forms of energy.
Next, we calculate the light output power of the LED lamp based on the power and luminous efficiency. The light output power Plight can be expressed as:
Plight =P×η
Substituting the known $P$ and $\eta$ into the above formula, we get:
Plight =10×80%=10×0.8=8W
Therefore, the light output power of the LED lamp is 8W. This means that the light energy that the LED lamp can output per second is 8 joules.