A : Optical and radio telescopes are built on the ground but X-ray astronomy is possible only from satellites orbiting the earth.
R : Atmosphere absorbs X-rays, while visible and radiowaves can penetrate it.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1)
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2)
C. If assertion is true statement but Reason is false, then mark (3)
D. If both Assertion and Reason are false statements, then mark (4)

Answer

To analyze the assertion (A) and reason (R) provided in the question, we can break down the information step by step.

### Step 1: Understanding the Assertion (A)
The assertion states that optical and radio telescopes are built on the ground, while X-ray astronomy is only possible from satellites orbiting the Earth.

**Explanation**:
- Optical telescopes use visible light to observe celestial objects and can be placed on the ground because visible light can penetrate the Earth's atmosphere.
- Radio telescopes utilize radio waves, which also penetrate the atmosphere effectively, allowing them to be ground-based.
- X-ray astronomy, however, requires observation of X-rays, which do not penetrate the atmosphere well.

### Step 2: Understanding the Reason (R)
The reason states that the atmosphere absorbs X-rays, while visible and radio waves can penetrate it.

**Explanation**:
- The Earth's atmosphere is opaque to X-rays, meaning that X-rays are absorbed by the atmosphere and do not reach the surface. This is why X-ray telescopes must be placed in space, above the atmosphere.
- In contrast, visible light and radio waves can pass through the atmosphere without significant absorption, allowing ground-based telescopes to function effectively.

### Step 3: Conclusion
Both the assertion (A) and the reason (R) are correct. The assertion accurately describes the situation regarding the placement of telescopes, and the reason provides a valid explanation for why X-ray astronomy must be conducted from space.

### Final Answer
Both A and R are correct, and R is the correct explanation of A.

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