A : In Young.s double slit experiment, we observe an interference pattern on the screen if both the slits are illuminated by two bulbs of same power.
R : The interference pattern is obserbed only when source are monochromatic.

Options

A. Both A and R are true and R is the correct explanation of A
B. Both A and R are true and R is not the correct explanation of A
C. A is true and R is false
D. Both A and R are false

Answer

To analyze the given statements regarding Young's double slit experiment, we will evaluate the assertion (A) and the reason (R) step by step.

### Step 1: Understanding the Assertion (A)
The assertion states: "In Young's double slit experiment, we observe an interference pattern on the screen if both the slits are illuminated by two bulbs of the same power."

- In Young's double slit experiment, an interference pattern is indeed produced when light waves from two slits overlap on a screen. However, the key requirement for observing a clear interference pattern is that the light sources must be coherent. Coherent sources have a constant phase difference and the same frequency and wavelength.

### Step 2: Evaluating the Assertion
- The assertion is **incomplete** because it does not mention the necessity of coherence between the light sources. Therefore, while it is true that we can observe an interference pattern, the condition of coherence is essential, which is not stated in the assertion.

### Step 3: Understanding the Reason (R)
The reason states: "The interference pattern is observed only when sources are monochromatic."

- Monochromatic light means light of a single wavelength. While it is true that using monochromatic light is important for producing a stable interference pattern, it is not the only condition. The sources must also be coherent.

### Step 4: Evaluating the Reason
- The reason is also **incomplete** because it does not mention the requirement for coherence. Monochromatic light alone does not guarantee an interference pattern unless the sources are coherent.

### Conclusion
- Both the assertion (A) and the reason (R) are **false**. The assertion lacks the necessary condition of coherence, and the reason, while correct in emphasizing monochromatic light, also fails to mention coherence.

### Final Answer
Both the assertion and reason are false.

---