Assertion: To observe diffraction of light the size of obstacle/aperture should be of the order of `10^-7m`.
Reason: `10^-7m` is the order of wavelength of visible light.

Options

A. (a) If both assertion and reason are true and reason is the correct explanation of assertion.
B. (b) If both assertion and reason are true but reason is not the correct explanation of assertion.
C. (c) If assertion is true but reason is false.
D. (d) If assertion and reason both are false.

Explanation

To analyze the assertion and reason provided in the question, we can break down the solution into the following steps:

### Step 1: Understanding Diffraction
Diffraction is a phenomenon that occurs when light waves encounter an obstacle or aperture that is comparable in size to their wavelength. It results in the bending and spreading of waves.

### Step 2: Wavelength of Visible Light
The wavelength of visible light typically ranges from about \( 4 \times 10^{-7} \) m (400 nm) to \( 7 \times 10^{-7} \) m (700 nm). Therefore, the order of magnitude for the wavelength of visible light is indeed around \( 10^{-7} \) m.

### Step 3: Size of Aperture/Obstacle
To observe diffraction effects clearly, the size of the aperture or obstacle must be on the same order of magnitude as the wavelength of the light being used. This means that for visible light, the size of the aperture or obstacle should also be approximately \( 10^{-7} \) m.

### Step 4: Evaluating the Assertion and Reason
- **Assertion**: "To observe diffraction of light the size of obstacle/aperture should be of the order of \( 10^{-7} \) m." This is **True** because it aligns with the requirement for observing diffraction.

- **Reason**: "\( 10^{-7} \) m is the order of wavelength of visible light." This is also **True** as it accurately describes the wavelength range of visible light.

### Step 5: Conclusion
Both the assertion and the reason are true, and the reason correctly explains why the assertion is true. Therefore, we can conclude that the assertion is valid and supported by the reason.

### Final Answer:
Both the assertion and the reason are true, and the reason correctly explains the assertion.

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