A : The apparent depth of a tank of water decreases if viewed obliquely.
R : Real depth decreases if viewed obliquely.

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 given assertion and reason, we can break down the solution into the following steps:

### Step 1: Understand the Assertion
The assertion states that "the apparent depth of a tank of water decreases if viewed obliquely." This means that when we look at the water tank from an angle rather than straight down, the depth we perceive (apparent depth) appears to be less than the actual depth.

**Hint:** Consider how light travels from the water to our eyes and how angles affect our perception of depth.

### Step 2: Understand the Reason
The reason states that "real depth decreases if viewed obliquely." Real depth refers to the actual physical depth of the water in the tank. This statement implies that the actual depth changes based on the angle of view, which is incorrect.

**Hint:** Think about the definition of real depth and whether it can change based on viewing angle.

### Step 3: Analyze the Real Depth
Real depth is a fixed quantity that does not change regardless of the observer's position. It is the actual distance from the surface of the water to the bottom of the tank. Therefore, the reason provided is incorrect.

**Hint:** Remember that physical properties like depth do not change with perspective; they remain constant.

### Step 4: Analyze the Apparent Depth
When viewed obliquely, the light rays from the bottom of the tank bend due to refraction as they pass from water to air. This bending causes the observer to perceive a shallower depth than the actual depth. Thus, the assertion is correct.

**Hint:** Consider the principles of refraction and how they affect our perception of objects submerged in water.

### Step 5: Conclusion
Based on the analysis:
- The assertion is correct: the apparent depth decreases when viewed obliquely.
- The reason is incorrect: the real depth does not change with the angle of view.

Thus, the correct conclusion is that the assertion is true, but the reason is false.

**Final Answer:** Assertion (A) is true, and Reason (R) is false.