Water rises upto 10 cm height in a long capillary tube. If this tube is immersed in water so that the height above the water surface is only 8 cm, then

Options

A. water flows out continuously from the upper end
B. water rises upto upper end and forms a spherical surface
C. water only rises upto 6 cm height
D. water does not rise at all

Explanation

To solve the problem, we need to analyze the behavior of water in a capillary tube when it is partially submerged in water. Here’s a step-by-step solution:

### Step 1: Understand Capillary Action
Capillary action is the ability of a liquid to flow in narrow spaces without the assistance of external forces. In this case, water rises in the capillary tube due to adhesive forces between the water molecules and the tube's walls.

### Step 2: Initial Conditions
The problem states that water rises to a height of 10 cm in the capillary tube when it is not submerged. This height is determined by the balance of cohesive and adhesive forces acting on the water.

### Step 3: Immersion of the Tube
When the capillary tube is immersed in water such that the height of the tube above the water surface is only 8 cm, we need to analyze how this affects the water level inside the tube.

### Step 4: Analyzing the New Situation
Since the capillary tube is now partially submerged, the water inside the tube will be influenced by the surrounding water level. The maximum height the water can rise in the tube (10 cm) is now limited by the external water level (which is 8 cm above the water surface).

### Step 5: Determine the Water Level Inside the Tube
The water inside the capillary tube cannot rise above the level of the surrounding water. Therefore, the water level inside the tube will adjust to match the external water level, which is 8 cm.

### Step 6: Evaluate the Options
- **Option A**: Water flows out continuously from the upper end - This is false because the water level inside the tube is at 8 cm, which is below the maximum height of 10 cm.
- **Option B**: Water rises to the upper end and forms a spherical surface - This is true because the water level inside the tube will rise to 8 cm, forming a meniscus.
- **Option C**: Water only rises up to 6 cm height - This is false because the water rises to 8 cm.
- **Option D**: Water does not rise at all - This is false because the water does rise to 8 cm.

### Conclusion
The correct option is **B**: Water rises to the upper end and forms a spherical surface.

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