Assertion: The temperature of the surface of the sun is approximately `6000 K`. If we take a big lens and focus the sun rays, we can produce a temperature at `8000 K`
Reason: This highest temperature can be produced according to second law of thermodynamics.

Answer

To solve the problem, we need to analyze both the assertion and the reason provided in the question.

### Step 1: Analyze the Assertion
The assertion states that the temperature of the surface of the sun is approximately 6000 K and that by focusing sunlight with a big lens, we can produce a temperature of 8000 K.

**Analysis**:
- The temperature of the sun's surface is indeed around 6000 K.
- However, focusing sunlight does not inherently increase the temperature beyond the maximum temperature of the source (in this case, the sun).

### Step 2: Evaluate the Claim of Producing 8000 K
The assertion claims that we can achieve a temperature of 8000 K by focusing sunlight.

**Analysis**:
- According to the laws of thermodynamics, specifically the second law, it is not possible to create a temperature higher than the source temperature (6000 K) without external work or energy input.

### Step 3: Analyze the Reason
The reason states that the highest temperature can be produced according to the second law of thermodynamics.

**Analysis**:
- The second law of thermodynamics indicates that heat cannot spontaneously flow from a colder body to a hotter body. It also implies that without external work, one cannot achieve a temperature higher than the source temperature.

### Step 4: Conclusion
Both the assertion and the reason are incorrect. The assertion incorrectly suggests that a temperature of 8000 K can be achieved by simply focusing sunlight, and the reason incorrectly states that this can be done according to the second law of thermodynamics.

### Final Answer
- **Assertion**: Incorrect
- **Reason**: Incorrect